Display device and electronic apparatus

ABSTRACT

[Object] It is possible to further improve reliability. 
     [Solution] There is provided a display device including: a pixel unit which is configured with a plurality of pixel circuits arranged in a matrix, each of the pixel circuits including a light emitting element and a driving circuit for driving the light emitting element; scanning lines which are interconnections connected to the respective pixel circuits and are provided to extend in a first direction and correspond to respective rows of a plurality of the pixel circuits; and signal lines which are interconnections connected to the respective pixel circuits and are provided to extend in a second direction orthogonal to the first direction and correspond to respective columns of a plurality of the pixel circuits. One of the scanning lines and the signal lines, provided for the one pixel circuit, which is larger in number is positioned in a lower-level interconnection layer. An electrode of a capacitance element included in the driving circuit is positioned in the interconnection layer in which either the scanning lines or the signal lines are provided.

TECHNICAL FIELD

The present disclosure relates to a display device and an electronicapparatus.

BACKGROUND ART

A display device drivable by what is called an active matrix systemusually has a configuration in which a light emitting element and apixel circuit including a driving circuit for causing the light emittingelement to be driven are provided in a position corresponding to each ofthe points of intersection of a plurality of scanning lines that extendalong a lateral direction (hereinafter, occasionally referred to as ahorizontal direction) of a display surface and are placed to be arrangedin an upright direction (hereinafter, occasionally referred to as avertical direction) of the display surface and a plurality of data lines(signal lines) that extend along the vertical direction and are placedto be arranged in the horizontal direction. One pixel circuitcorresponds to one pixel or sub-pixel. The electric potentials of thescanning line and the signal line are changed at appropriate timings;thereby, the on/off of an active element (a transistor or the like)provided in the driving circuit in the pixel circuit is controlled asappropriate, and the light emission of the light emitting element in thepixel circuit is controlled. As a display device drivable by an activematrix system, for example, a display device in which an organic lightemitting diode (OLED) is used as a light emitting element (hereinafter,occasionally referred to as an organic electroluminescence (EL) displaydevice) is developed (for example, Patent Literatures 1 to 4).

CITATION LIST Patent Literature

Patent Literature 1: JP 2015-55763A

Patent Literature 2: JP 2016-53636A

Patent Literature 3: JP 2016-53640A

Patent Literature 4: JP 2016-53641A

DISCLOSURE OF INVENTION Technical Problem

Here, in a display device, for example, in order to realize a displaywith higher definition and to mount it in a relatively small-sizedelectronic apparatus such as a wearable device, pixel size needs to bereduced. When pixel size is reduced, a layout of a pixel circuit is alsominiaturized, and thus the following problems may occur. That is, theproblems are deterioration of emission luminance uniformity caused bynoise interference between electrodes due to an increase in parasiticcapacitance between interconnections, deterioration of luminanceuniformity caused by deterioration of noise resistance due to thepressure of the area of an electrode of a capacitance element, a failureof a short circuit between interconnections due to a pixelinterconnection becoming dense, a failure of interconnection open due toan interconnection pattern having a small area not being formed normally(so-called film skipping), and the like. In order to realize a displaydevice with high definition and higher reliability, it is necessary tosuppress the occurrence of these problems.

Consequently, the present disclosure proposes a new and improved displaydevice and electronic apparatus which are capable of further improvingreliability.

Solution to Problem

According to the present disclosure, there is provided a display deviceincluding a pixel unit which is configured with a plurality of pixelcircuits arranged in a matrix, each of the pixel circuits including alight emitting element and a driving circuit for driving the lightemitting element, scanning lines which are interconnections connected tothe respective pixel circuits and are provided to extend in a firstdirection and correspond to respective rows of a plurality of the pixelcircuits, and signal lines which are interconnections connected to therespective pixel circuits and are provided to extend in a seconddirection orthogonal to the first direction and correspond to respectivecolumns of a plurality of the pixel circuits, in which one of thescanning lines and the signal lines, provided for the one pixel circuit,which is larger in number is positioned in a lower-level interconnectionlayer, and an electrode of a capacitance element included in the drivingcircuit is positioned in the interconnection layer in which either thescanning lines or the signal lines are provided.

In addition, according to the present disclosure, there is also providedan electronic apparatus including a display device which performsdisplay on the basis of a video signal, in which the display deviceincludes a pixel unit which is configured with a plurality of pixelcircuits arranged in a matrix, each of the pixel circuits including alight emitting element and a driving circuit for driving the lightemitting element, scanning lines which are interconnections connected tothe respective pixel circuits and are provided to extend in a firstdirection and correspond to respective rows of a plurality of the pixelcircuits, and signal lines which are interconnections connected to therespective pixel circuits and are provided to extend in a seconddirection orthogonal to the first direction and correspond to respectivecolumns of a plurality of the pixel circuits, one of the scanning linesand the signal lines, provided for the one pixel circuit, which islarger in number is positioned in a lower-level interconnection layer,and an electrode of a capacitance element included in the drivingcircuit is positioned in the interconnection layer in which either thescanning lines or the signal lines are provided.

According to the present disclosure, with respect to two types oforthogonal interconnections (scanning lines and signal lines) providedfor a pixel unit, one of the two types of interconnections, provided forone pixel circuit, which is larger in number is formed in a lower-levelinterconnection layer. Therefore, it is possible to make aninterconnection pattern in a higher-level interconnection layerrelatively sparse. In addition, an electrode of a capacitance elementincluded in the pixel circuit is formed in an interconnection layer inwhich any one of the two types of interconnections is provided. That is,since the electrode of the capacitance element can be provided in aninterconnection layer having a relatively sparse interconnectionpattern, it is possible the degree of freedom of arrangement of theelectrode is improved and to sufficiently secure the area of theelectrode. Therefore, it is possible to solve a problem caused to arelatively dense interconnection pattern, a problem caused by the areaof the electrode of the capacitance element which is incapable of beingsufficiently secured, and the like. Accordingly, a display device withhigher reliability can be realized.

Advantageous Effects of Invention

As described above, according to the present disclosure, it is possibleto further improve reliability. Note that the effects described aboveare not necessarily limitative. With or in the place of the aboveeffects, there may be achieved any one of the effects described in thisspecification or other effects that may be grasped from thisspecification.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing an overall configuration of adisplay device according to the present embodiment.

FIG. 2 is a schematic diagram showing a configuration of a pixel unit, ascanning unit, and a selection unit shown in FIG. 1, in more detail.

FIG. 3 is a schematic diagram showing a configuration example of a pixelcircuit shown in FIG. 2.

FIG. 4 is a diagram for describing operation of the pixel circuitaccording to the present embodiment.

FIG. 5 is a schematic diagram showing another configuration example ofthe pixel circuit according to the present embodiment.

FIG. 6 is a schematic cross-sectional view showing a stacked structureof the pixel circuit.

FIG. 7 is a diagram for describing an example of a layout of aninterconnection layer according to the present embodiment.

FIG. 8 is a diagram for comparison with the layout shown in FIG. 7, andis a diagram showing an example of a layout in a case in which an Hscanning line and a V signal line are formed in an interconnection layerdifferent from that in the present embodiment, in a case in which an Hscanning line and a V signal line are formed in a first interconnectionlayer and a second interconnection layer.

FIG. 9 is a diagram for describing another example of a layout of theinterconnection layer according to the present embodiment.

FIG. 10 is a diagram for comparison with the layout shown in FIG. 9, andis a diagram showing an example of a layout in a case in which an Hscanning line and a V signal line are formed in an interconnection layerdifferent from that in the present embodiment, in a case in which an Hscanning line and a V signal line are formed in a first interconnectionlayer, a second interconnection layer, and a third interconnectionlayer.

FIG. 11 is a diagram showing an example of arrangement of third vias inthree sub-pixels in a case in which one pixel is formed in the threesub-pixels.

FIG. 12 is a diagram showing an example of arrangement of third vias infour sub-pixels in a case in which one pixel is formed in the foursub-pixels.

FIG. 13 is a cross-sectional view showing a specific configurationexample of the display device according to the present embodiment.

FIG. 14 is a diagram showing an external appearance of a smartphone thatis an example of an electronic apparatus in which the display deviceaccording to the present embodiment can be used.

FIG. 15 is a diagram showing an external appearance of a digital camerathat is another example of an electronic apparatus in which the displaydevice according to the present embodiment can be used.

FIG. 16 is a diagram showing an external appearance of a digital camerathat is another example of an electronic apparatus in which the displaydevice according to the present embodiment can be used.

FIG. 17 is a diagram showing an external appearance of a head-mounteddisplay that is another example of an electronic apparatus in which thedisplay device according to the present embodiment can be used.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, (a) preferred embodiment (s) of the present disclosure willbe described in detail with reference to the appended drawings. Notethat, in this specification and the appended drawings, structuralelements that have substantially the same function and structure aredenoted with the same reference numerals, and repeated explanation ofthese structural elements is omitted.

Note that, in the drawings, the sizes etc. of some layers in thecross-sectional view and some areas in the top view showing a layout maybe expressed exaggeratedly for the sake of description. The relativesizes of layers, areas, etc. shown in the drawings do not necessarilyexpress the actual magnitude relationships between layers, areas, etc.accurately.

Further, in the following, an embodiment in which the display device isan organic EL display device is described as an example of the presentdisclosure. However, the present disclosure is not limited to thisexample, and the display device that is an object of the presentdisclosure may be various display devices as long as they are displaydevices drivable by an active matrix-type driving system.

Note that the description is given in the following order.

1. Overall configuration of display device

2. Configuration of pixel circuit

3. Operation of pixel circuit

4. Layout of interconnection layer

5. Specific configuration example of display device

6. Application examples

7. Supplement

(1. Overall Configuration of Display Device)

An overall configuration of a display device according to an embodimentof the present disclosure will now be described with reference to FIGS.1 and 2. FIG. 1 is a schematic diagram showing an overall configurationof a display device according to the present embodiment. FIG. 2 is aschematic diagram showing the configuration of a pixel unit, a scanningunit, and a selection unit shown in FIG. 1, in more detail.

Referring to FIG. 1, in a display device 1 according to the presentembodiment, a pixel unit 20, a scanning unit 30, and a selection unit 40are arranged on a display panel 10. As shown in FIG. 2, in the pixelunit 20, a plurality of pixel circuits 210 are arranged in a matrixform. Note that, although written as the pixel circuit 210 for the sakeof convenience, “the pixel circuit 210” shown in FIG. 2 shows a portionexcluding an interconnection layer of the pixel circuit 210; inpractice, in the pixel circuit 210, interconnections (interconnectionsextending from the scanning unit 30 and the selection unit 40, a powersupply line 332, etc. described later) may be connected to “the pixelcircuit 210” shown in FIG. 2. That is, these interconnections may beprovided in common to a plurality of pixel circuits 210, but they canalso be parts of the pixel circuit 210; thus, in FIG. 2, a portionexcluding the interconnection layer of the pixel circuit 210 is shown asthe pixel circuit 210 for the sake of convenience. In the presentspecification, in a case of being written as “the pixel circuit 210,”this component may thus refer to only a portion excluding theinterconnection layer of the pixel circuit 210 for the sake ofconvenience.

One pixel circuit 210 corresponds to one sub-pixel. Here, the displaydevice 1 is a display device capable of color display, and one pixelserving as a unit that forms a color image includes a plurality ofsub-pixels. Specifically, one pixel includes three sub-pixels of asub-pixel that emits red light, a sub-pixel that emits green light, anda sub-pixel that emits blue light. In FIG. 2, a color (R, G, or B)corresponding to each sub-pixel is simulatively written in each pixelcircuit 210. Light emission in each pixel circuit 210 (that is, eachsub-pixel) is controlled as appropriate, and thereby a desired image isdisplayed in the pixel unit 20. Thus, the pixel unit 20 corresponds to adisplay surface in the display device 1.

However, in the present embodiment, the combination of sub-pixelsincluded in one pixel is not limited to a combination of sub-pixels ofthree primary colors of RGB. For example, in one pixel, sub-pixels ofone color or a plurality of colors may further be added to sub-pixels ofthree primary colors. Specifically, for example, in one pixel, asub-pixel that emits white light may be added to sub-pixels of threeprimary colors in order to improve the luminance; or in one pixel, atleast one sub-pixel that emits light of a complementary color may beadded to sub-pixels of three primary colors in order to expand the colorreproduction range. Alternatively, in the display device 1, a sub-pixelmay not exist, and one pixel circuit 210 may correspond to one pixel.Furthermore, alternatively, the display device 1 may not be one capableof color display, and may be one that performs monochrome display.

The scanning unit 30 is placed on one side in the horizontal directionof the pixel unit 20. A plurality of interconnections that are providedto be arranged in the vertical direction extend in the horizontaldirection from the scanning unit 30 toward the pixel unit 20.Specifically, as shown in FIG. 2, the scanning unit 30 includes awriting scanning unit 301, a first driving scanning unit 311, and asecond driving scanning unit 321. A plurality of writing scanning lines302 extend from the writing scanning unit 301 toward the respective rowsof the pixel circuits 210, a plurality of first driving lines 312 extendfrom the first driving scanning unit 311 toward the respective rows ofthe pixel circuits 210, and a plurality of second driving lines 322extend from the second driving scanning unit 321 toward the respectiverows of the pixel circuits 210. Each of the plurality ofinterconnections (the writing scanning lines 302, the first drivinglines 312, and the second driving lines 322) is connected to therespective pixel circuits 210. The writing scanning unit 301, the firstdriving scanning unit 311, and the second driving scanning unit 321change the electric potentials of these plurality of interconnections asappropriate, and thereby control the operation of each pixel circuit 210so that a desired image can be displayed as the entire display surface.Details of the connection state between the writing scanning line 302,the first driving line 312, and the second driving line 322, and thepixel circuit 210, and functions of the writing scanning unit 301, thefirst driving scanning unit 311, and the second driving scanning unit321 are described later with reference to FIG. 3.

The selection unit 40 is placed on one side in the vertical direction ofthe pixel unit 20. A plurality of interconnections that are provided tobe arranged in the horizontal direction extend in the vertical directionfrom the selection unit 40 toward the pixel unit 20. Specifically, asshown in FIG. 2, the selection unit 40 includes a signal output unit401. A plurality of signal lines 402 extend from the signal output unit401 toward the respective columns of the pixel circuits 210. Each of theplurality of signal lines 402 is connected to the respective pixelcircuits 210 in the pixel unit 20. The signal output unit 401 changesthe electric potentials of the plurality of signal lines 402 asappropriate, and thereby controls the operation of each pixel circuit210 so that a desired image can be displayed as the entire displaysurface. Details of the connection state between the signal line 402 andthe pixel circuit 210, and functions of the signal output unit 401 aredescribed later with reference to FIG. 3.

Thus, interconnections extending in the horizontal direction from thescanning unit 30 are provided to correspond to the respective rows ofthe pixel circuits 210 arranged in a matrix form, and are connected tothe respective pixel circuits 210. Further, interconnections extendingin the vertical direction from the selection unit 40 are provided tocorrespond to the respective columns of the pixel circuits 210 arrangedin a matrix form, and are connected to the respective pixel circuits210. Then, the electric potentials of the plurality of interconnectionsare changed by the scanning unit 30 and the selection unit 40 asappropriate, and thereby the operation of each pixel circuit 210 of thepixel unit 20 is controlled.

(2. Configuration of Pixel Circuit)

The configuration of the pixel circuit 210 shown in FIG. 2 will now bedescribed with reference to FIG. 3. FIG. 3 is a schematic diagramshowing the configuration of the pixel circuit 210 shown in FIG. 2. FIG.3 shows a circuit configuration of one pixel circuit 210 among theplurality of pixel circuits 210 shown in FIG. 2, and shows theconnection state with respect to the pixel circuit 210 of the writingscanning line 302, the first driving line 312, the second driving line322, and the signal line 402.

As shown in FIG. 3, the pixel circuit 210 includes an organic lightemitting diode 211 that is a light emitting element and a drivingcircuit that drives the organic light emitting diode 211 by passing acurrent through the organic light emitting diode 211. The drivingcircuit includes four transistors that are active elements (a drivingtransistor 212, a sampling transistor 213, a light emission controltransistor 214, and a switching transistor 217) and capacitance elements(a holding capacitance 215 and an auxiliary capacitance 216). In thepixel circuit 210, interconnections (the writing scanning line 302, thefirst driving line 312, the second driving line 322, and the signal line402 mentioned above, a power supply line 332 described later, etc.) areconnected to these elements.

Note that an organic light emitting diode having an ordinary structuremay be used as the organic light emitting diode 211. Further, each ofthe driving transistor 212, the sampling transistor 213, the lightemission control transistor 214, and the switching transistor 217 is aP-channel four-terminal (source/gate/drain/back gate) transistor formedon a semiconductor such as silicon (Si), and the structure may besimilar to an ordinary P-channel four-terminal transistor. Therefore, adetail description of the structures of the organic light emitting diode211, the driving transistor 212, the sampling transistor 213, the lightemission control transistor 214, and the switching transistor 217 isomitted herein.

The cathode of the organic light emitting diode 211 is connected to acommon power supply line 331 (electric potential: V_(CATH)) that isprovided in common to all the pixel circuits 210 of the pixel unit 20.The drain electrode of the driving transistor 212 is connected to theanode of the organic light emitting diode 211.

The drain electrode of the light emission control transistor 214 isconnected to the source electrode of the driving transistor 212, and thesource electrode of the light emission control transistor 214 isconnected to a power supply line 332 (electric potential: V_(cc); V_(cc)being the power supply potential). Further, the gate electrode of thedriving transistor 212 is connected to the drain electrode of thesampling transistor 213, and the source electrode of the samplingtransistor 213 is connected to the signal line 402.

Therefore, by the sampling transistor 213 being brought into aconduction state, an electric potential corresponding to the electricpotential of the signal line 402 is applied to the gate electrode of thedriving transistor 212 (the electric potential of the signal line 402 iswritten), and the driving transistor 212 is brought into a conductionstate. Further, in this event, by the light emission control transistor214 being brought into a conduction state, an electric potentialcorresponding to the signal potential V_(cc) is applied to the sourceelectrode of the driving transistor 212, and a drain-source currentI_(ds) is generated in the driving transistor 212; thus, the organiclight emitting diode 211 is driven. In this event, the magnitude of thedrain-source current I_(ds) changes in accordance with the gatepotential V_(g) of the driving transistor 212, and therefore theemission luminance of the organic light emitting diode 211 is controlledin accordance with the gate potential V_(g) of the driving transistor212, that is, the electric potential of the signal line 402 written bythe sampling transistor 213.

Thus, the driving transistor 212 has the function of causing the organiclight emitting diode 211 to be driven by the drain-source current I_(ds)of the driving transistor 212. Further, the sampling transistor 213controls the gate voltage of the driving transistor 212 in accordancewith the electric potential of the signal line 402, that is, controlsthe on/off of the driving transistor 212; thus, the sampling transistor213 has the function of writing the electric potential of the signalline 402 on the pixel circuit 210 (that is, has the function of samplinga pixel circuit 210 to write the electric potential of the signal line402 on). Further, the light emission control transistor 214 controls theelectric potential of the source electrode of the driving transistor212, and thereby controls the drain-source current I_(ds) of the drivingtransistor 212; thus, the light emission control transistor 214 has thefunction of controlling the light emission/non-light emission of theorganic light emitting diode 211.

The holding capacitance 215 is connected between the gate electrode ofthe driving transistor 212 (that is, the drain electrode of the samplingtransistor 213) and the source electrode of the driving transistor 212.That is, the holding capacitance 215 holds the gate-source voltageV_(gs) of the driving transistor 212. The auxiliary capacitance 216 isconnected between the source electrode of the driving transistor 212 andthe power supply line 332. The auxiliary capacitance 216 has the actionof suppressing the source potential of the driving transistor 212varying when the electric potential of the signal line 402 is written.

The signal output unit 401 controls the electric potential of the signalline 402 (a signal line voltage Date) as appropriate, and thereby writesthe electric potential of the signal line 402 on the pixel circuit 210(specifically, as described above, the electric potential of the signalline 402 is written on a pixel circuit 210 selected by the samplingtransistor 213). In the present embodiment, the signal output unit 401selectively outputs a signal voltage V_(sig) corresponding to a videosignal, a first reference voltage V_(ref), and a second referencevoltage V_(ofs) via the signal line 402. Here, the first referencevoltage V_(ref) is a reference voltage for causing the organic lightemitting diode 211 to be extinguished reliably. Further, the secondreference voltage V_(ofs) is a voltage serving as a reference of thesignal voltage V_(sig) corresponding to a video signal (for example, avoltage equivalent to the black level of a video signal), and is usedwhen performing a threshold correction operation described later.

The writing scanning line 302 is connected to the gate electrode of thesampling transistor 213. The writing scanning unit 301 controls theon/off of the sampling transistor 213 by changing the electric potentialof the writing scanning line 302 (a scanning line voltage WS), andexecutes the processing of writing the electric potential of the signalline 402 described above (for example, the signal voltage V_(sig)corresponding to a video signal) on the pixel circuit 210. In practice,as described with reference to FIG. 2, a plurality of writing scanninglines 302 are extended to the respective rows of a plurality of pixelcircuits 210 arranged in a matrix form. When writing the electricpotential of the signal line 402 on each pixel circuit 210, the writingscanning unit 301 sequentially supplies the scanning line voltage WS ofa prescribed value to the plurality of writing scanning lines 302, andthereby scans the pixel circuits 210 on a row basis one after another.

Note that, also for the signal line 402, in practice a plurality ofsignal lines 402 are extended to the respective columns of a pluralityof pixel circuits 210 arranged in a matrix form, as described withreference to FIG. 2. The signal voltage V_(sig) corresponding to a videosignal, the first reference voltage V_(ref), and the second referencevoltage V_(ofs), which are alternatively outputted from the signaloutput unit 401, are written on the pixel circuits 210 via the pluralityof signal lines 402, in units of pixel rows selected by scanning by thewriting scanning unit 301. That is, the signal output unit 401 writesthe electric potential of the signal line 402 on a row basis.

The first driving line 312 is connected to the gate electrode of thelight emission control transistor 214. The first driving scanning unit311 controls the on/off of the light emission control transistor 214 bychanging the electric potential of the first driving line 312 (a firstdriving line voltage DS), and executes the processing of controlling thelight emission/non-light emission of the organic light emitting diode211 described above. In practice, as described with reference to FIG. 2,a plurality of first driving lines 312 are extended to the respectiverows of a plurality of pixel circuits 210 arranged in a matrix form. Insynchronization with scanning by the writing scanning unit 301, thefirst driving scanning unit 311 sequentially supplies the first drivingline voltage DS of a prescribed value to the plurality of first drivinglines 312, and thereby controls the light emission/non-light emission ofeach pixel circuit 210 as appropriate.

Here, further, in the pixel circuit 210, the source electrode of theswitching transistor 217 is connected to the anode of the organic lightemitting diode 211. The drain electrode of the switching transistor 217is connected to a ground line 333 (electric potential: V_(ss); V_(ss)being the ground potential). A current flowing through the drivingtransistor 212 during the non-light emission period of the organic lightemitting diode 211 flows through the ground line 333 by means of acurrent path formed by the switching transistor 217.

Here, as described later, when driving the pixel circuit 210 accordingto the present embodiment, a threshold correction operation thatcorrects the threshold voltage V_(th) of the driving transistor 212 isperformed, and further a threshold correction preparation operation isperformed as a pre-stage for performing the threshold correctionoperation. In the threshold correction preparation operation, anoperation that initializes the gate potential V_(g) and the sourcepotential V_(s) of the driving transistor 212 is performed, andconsequently the gate-source voltage V_(gs) of the driving transistor212 becomes larger than the threshold voltage V_(th) of the drivingtransistor 212. This is because, if the gate-source voltage V_(gs) ofthe driving transistor 212 is not set larger than the threshold voltageV_(th) of the driving transistor 212, the threshold correction operationcannot be performed properly.

Therefore, if the operation that initializes the gate potential V_(g)and the source potential V_(s) of the driving transistor 212 mentionedabove is performed, a situation where the anode potential V_(ano) of theorganic light emitting diode 211 exceeds the threshold voltage V_(the1)of the organic light emitting diode 211 in spite of the non-lightemission period of the organic light emitting diode 211 may occur.Consequently, a current flows into the organic light emitting diode 211from the driving transistor 212, and a phenomenon in which the organiclight emitting diode 211 emits light in spite of the non-light emissionperiod occurs.

Thus, in the present embodiment, a current circuit using the switchingtransistor 217 described above is provided in order to prevent such aphenomenon. Thereby, the current from the driving transistor 212mentioned above does not flow into the organic light emitting diode 211but flows into this current circuit, and unintentional light emission ofthe organic light emitting diode 211 can be prevented.

The second driving line 322 is connected to the gate electrode of theswitching transistor 217. The second driving scanning unit 321 controlsthe on/off of the switching transistor 217 by changing the electricpotential of the second driving line 322 (a second driving line voltageAZ). Specifically, the second driving scanning unit 321 changes thesecond driving line voltage AZ as appropriate, and thereby sets theswitching transistor 217 in a conduction state and opens the currentcircuit described above during a light-emission-receiving period, morespecifically, at least during a period in which the gate-source voltageV_(gs) of the driving transistor 212 is set larger than the thresholdvoltage V_(th) of the driving transistor 212 by performing the thresholdcorrection preparation operation. In practice, as described withreference to FIG. 2, a plurality of second driving lines 322 areextended to the respective rows of a plurality of pixel circuits 210arranged in a matrix form. The second driving scanning unit 321sequentially supplies the second driving line voltage AZ of a prescribedvalue to the plurality of second driving lines 322 in synchronizationwith scanning by the writing scanning unit 301, and thereby controls thedriving of the switching transistor 217 so that the switching transistor217 is in a conduction state during the period mentioned above, asappropriate.

Note that the writing scanning unit 301, the first driving scanning unit311, the second driving scanning unit 321, and the signal output unit401 can be obtained using known techniques by means of various circuitscapable of achieving the functions described above, such as a shiftregister circuit, and therefore a description of detailed circuitconfigurations of these units is omitted herein.

Hereinabove, the configuration of the pixel circuit 210 according to thepresent embodiment is described.

(3. Operation of Pixel Circuit)

The operation of the pixel circuit 210 described hereinabove will now bedescribed. FIG. 4 is a diagram for describing the operation of the pixelcircuit 210 according to the present embodiment. FIG. 4 shows a timingwaveform diagram of signals related to the operation of the pixelcircuit 210. Specifically, FIG. 4 shows manners of changes in onehorizontal period (one H-period) of the electric potential of the signalline 402 (the signal line voltage Date), the electric potential of thewriting scanning line 302 (the scanning line voltage WS), the electricpotential of the first driving line 312 (the first driving line voltageDS), the electric potential of the second driving line 322 (the seconddriving line voltage AZ), the source potential V_(s) of the drivingtransistor 212, and the gate potential V_(g) of the driving transistor212.

It is noted that, since each of the sampling transistor 213, the lightemission control transistor 214, and the switching transistor 217 is ofa P-channel type, these transistors are in an ON state, that is, aconduction state when the scanning line voltage WS, the first drivingline voltage DS, and the second driving line voltage AZ are in a lowelectric potential state, respectively, and these transistors are in anoff state, that is, a non-conduction state when the scanning linevoltage WS, the first driving line voltage DS, and the second drivingline voltage AZ are in a high electric potential state, respectively.Also for the driving transistor 212, similarly, the driving transistor212 is in a conduction state in a case where the gate potential V_(g) isa low electric potential, and the driving transistor 212 is in anon-conduction state in a case where the gate potential V_(g) is a highelectric potential. Further, as described above, any of the signalvoltage V_(sig) corresponding to a video signal, the first referencevoltage V_(ref), and the second reference voltage V_(ofs) isalternatively selected for the signal line voltage Date. In the waveformdiagram shown in FIG. 4, V_(ref)=V_(cc) (the power supply potential), asan example.

At the time of the ending of a light emission period of the organiclight emitting diode 211, the scanning line voltage WS transitions froma high electric potential to a low electric potential, and the samplingtransistor 213 is brought into a conduction state (time t₁). On theother hand, at time t₁, the signal line voltage Date is in a state ofbeing controlled to the first reference voltage V_(ref). Therefore, bythe transition of the scanning line voltage WS from a high electricpotential to a low electric potential, the gate-source voltage V_(gs) ofthe driving transistor 212 becomes less than or equal to the thresholdvoltage V_(th) of the driving transistor 212, and thus the drivingtransistor 212 is cut off. If the driving transistor 212 is cut off, thepath of current supply to the organic light emitting diode 211 is cutoff, and therefore the anode potential V_(ano) of the organic lightemitting diode 211 decreases gradually. With time, if the anodepotential V_(ano) becomes less than or equal to the threshold voltageV_(the1) of the organic light emitting diode 211, the organic lightemitting diode 211 enters a light extinction state completely (theperiod of time t₁ to time t₂; a light extinction period).

Subsequently to the light extinction period, a period in which apreparation operation (a threshold correction preparation operation)before performing a threshold correction operation described later isperformed is provided (the period of time t₂ to time t₃; a thresholdcorrection preparation period). Specifically, at time t₂, which is atiming at which the threshold correction preparation period is started,the scanning line voltage WS transitions from a high electric potentialto a low electric potential, and thereby the sampling transistor 213enters a conduction state. On the other hand, at time t₂, the signalline voltage Date is in a state of being controlled to the secondreference voltage V_(ofs). By the sampling transistor 213 entering aconduction state in a state where the signal line voltage Date is thesecond reference voltage V_(ofs), the gate potential V_(g) of thedriving transistor 212 becomes the second reference voltage V_(ofs).

Further, at time t₂, the first driving line voltage DS is in a lowelectric potential state, and the light emission control transistor 214is set in a conduction state. Therefore, the source potential V_(s) ofthe driving transistor 212 is the power supply voltage V_(cc). In thisevent, the gate-source voltage V_(gs) of the driving transistor 212 isV_(gs)=V_(ofs)−V_(cc).

Here, to perform the threshold correction operation, it is necessarythat the gate-source voltage V_(gs) of the driving transistor 212 be setlarger than the threshold voltage V_(th) of the driving transistor 212.Hence, each voltage value is set such that|V_(g)|=|V_(ofs)−V_(cc)|>|V_(th)|.

Thus, the initialization operation that sets the gate potential V_(g) ofthe driving transistor 212 to the second reference voltage V_(ofs) andsets the source potential V_(s) of the driving transistor 212 to thepower supply voltage V_(cc) is the threshold correction preparationoperation. That is, the second reference voltage V_(ofs) and the powersupply voltage V_(cc) are the initialization voltages of the gatepotential V_(g) and the source potential V_(s) of the driving transistor212, respectively.

If the threshold correction preparation period ends, next, the thresholdcorrection operation that corrects the threshold voltage V_(th) of thedriving transistor 212 is performed (the period of time t₃ to time t₄; athreshold correction period). In the period in which the thresholdcorrection operation is performed, first, at time t₃, which is thetiming at which the threshold correction period is started, the firstdriving line voltage DS transitions from a low electric potential to ahigh electric potential, and the light emission control transistor 214enters a non-conduction state. Thereby, the source potential V_(s) ofthe driving transistor 212 enters a floating state. On the other hand,at time t₃, the scanning line voltage WS is in a state of beingcontrolled to a high electric potential, and the sampling transistor 213is in a non-conduction state. Therefore, at time t₃, also the gatepotential V_(g) of the driving transistor 212 is in a floating state,and the source electrode and the gate electrode of the drivingtransistor 212 enter a state of being connected together via the holdingcapacitance 215, in a state of floating with each other. Thereby, asillustrated, the source potential V_(s) and the gate potential V_(g) ofthe driving transistor 212 gradually change to prescribed values inaccordance with the threshold voltage V_(th) of the driving transistor212.

Thus, the operation that, using the initialization voltage V_(ofs) ofthe gate potential V_(g) of the driving transistor 212 and theinitialization voltage V_(cc) of and the source potential V_(s) of thedriving transistor 212 as references, changes the source potential V_(s)and the gate potential V_(g) of the driving transistor 212 to prescribedvalues in accordance with the threshold voltage V_(th) of the drivingtransistor 212, in a floating state, is the threshold correctionoperation. If the threshold correction operation progresses, thegate-source voltage V_(gs) of the driving transistor 212 stabilizes tothe threshold voltage V_(th) of the driving transistor 212 with time. Avoltage equivalent to the threshold voltage V_(th) is held in theholding capacitance 215.

Here, as a matter of course, a design value exists for the thresholdvoltage V_(th) of the driving transistor 212; however, due tomanufacturing variations etc., the actual threshold voltage V_(th) doesnot always coincide with the design value. In this regard, by performinga threshold correction operation like the above, a voltage equivalent tothe actual threshold voltage V_(th) can be caused to be held in theholding capacitance 215 before the organic light emitting diode 211 iscaused to emit light. Thereby, after that, when causing the drivingtransistor 212 to be driven in order to cause the organic light emittingdiode 211 to emit light, a variation in the threshold voltage V_(th) ofthe driving transistor 212 can be canceled, as described later.Therefore, the driving of the driving transistor 212 can be controlledwith better precision, and a desired luminance can be obtained morefavorably.

If the threshold correction period ends, next, a signal writingoperation that writes the signal voltage V_(sig) corresponding to avideo signal is performed (the period of time t₄ to time t₅: a signalwriting period). In the signal writing period, at time t₄, which is thetiming at which the signal writing period is started, the scanning linevoltage WS transitions from a high electric potential to a low electricpotential, and the sampling transistor 213 is brought into a conductionstate. On the other hand, at time t₄, the signal line voltage Date is ina state of being controlled to the signal voltage V_(sig) in accordancewith a video signal, and therefore the signal voltage V_(sig) inaccordance with a video signal is written on the holding capacitance215. When writing the signal voltage V_(sig) corresponding to a videosignal, the auxiliary capacitance 216 connected between the sourceelectrode of the driving transistor 212 and the power supply line 332plays the role of suppressing the variation in the source potentialV_(s) of the driving transistor 212. Then, at the time when the signalvoltage V_(sig) in accordance with a video signal is written, that is,at the time when the signal voltage V_(sig) in accordance with a videosignal is applied to the gate electrode of the driving transistor 212and the driving transistor 212 is driven, the threshold voltage V_(th)of the driving transistor 212 is canceled by the voltage equivalent tothe threshold voltage V_(th) that is held in the holding capacitance 215as a result of the threshold correction operation. That is, by havingperformed the threshold correction operation mentioned above, thevariation in the threshold voltage V_(th) of the driving transistor 212between pixel circuits 210 is canceled.

At time t₅, the scanning line voltage WS transitions from a low electricpotential to a high electric potential, and the sampling transistor 213is brought into a non-conduction state; thereby, the signal writingperiod ends. If the signal writing period ends, next, a light emissionperiod is started from time t₆. At time t₆, which is the timing at whichthe light emission period is started, the first driving line voltage DStransitions from a high electric potential to a low electric potential,and thereby the light emission control transistor 214 is brought into aconduction state. Thus, a current is supplied from the power supply line332 having the power supply voltage V_(cc) to the source electrode ofthe driving transistor 212 via the light emission control transistor214.

In this event, due to the fact that the sampling transistor 213 is in anon-conduction state, the gate electrode of the driving transistor 212is electrically separated from the signal line 402, and is in a floatingstate. When the gate electrode of the driving transistor 212 is in afloating state, the holding capacitance 215 is connected between thegate and the source of the driving transistor 212, and thereby the gatepotential V_(g) varies in conjunction with the variation in the sourcepotential V_(s) of the driving transistor 212. That is, the sourcepotential V_(s) and the gate potential V_(g) of the driving transistor212 rise while holding the gate-source voltage V_(gs) held in theholding capacitance 215. Then, the source potential V_(s) of the drivingtransistor 212 rises up to a light emission voltage V_(oled) of theorganic light emitting diode 211 in accordance with the saturationcurrent of the transistor.

The operation in which the gate potential V_(g) of the drivingtransistor 212 varies in conjunction with the variation in the sourcepotential V_(s) in this way is referred to as a bootstrap operation. Inother words, the bootstrap operation is an operation in which the gatepotential V_(g) and the source potential V_(s) of the driving transistor212 vary while holding the gate-source voltage V_(gs) held in theholding capacitance 215, that is, the voltage between both ends of theholding capacitance 215.

Then, the drain-source current I_(d), of the driving transistor 212begins to flow through the organic light emitting diode 211, and therebythe anode potential V_(ano) of the organic light emitting diode 211rises in accordance with the drain-source current I_(ds). With time, ifthe anode potential V_(ano) of the organic light emitting diode 211exceeds the threshold voltage V_(the1) of the organic light emittingdiode 211, a driving current begins to flow through the organic lightemitting diode 211, and the organic light emitting diode 211 startslight emission.

The operations described hereinabove are executed in each pixel circuit210 within one H-period. Note that, as described above, the switchingtransistor 217 is one for preventing unintentional light emission of theorganic light emitting diode 211 that occurs due to a current flowingfrom the driving transistor 212 toward the organic light emitting diode211 in the non-light emission period; hence, the second driving linevoltage AZ is controlled so that the switching transistor 217 is in aconduction state in the non-light emission period, as appropriate. Inthe shown example, at time t₁ at which a light emission period ends, thesecond driving line voltage AZ transitions from a high electricpotential to a low electric potential; and immediately before time t₆ atwhich the next light emission period is ended or started, the seconddriving line voltage AZ transitions from a low electric potential to ahigh electric potential.

Note that, in regard to the overall configuration of the display device1, the configuration of the pixel circuit 210, and the operation of thepixel circuit 210 according to the present embodiment describedhereinabove, WO 2014/103500, which is a prior application by the presentapplicant, may be referred to except for the respects described later in(4. Layout of interconnection layer) below. In other words, the overallconfiguration of the display device 1, the configuration of the pixelcircuit 210, and the operation of the pixel circuit 210 according to thepresent embodiment may be similar to those described in WO 2014/103500except for the respects described later in (4. Layout of interconnectionlayer) below. However, what is described hereinabove is only an example,and the present embodiment is not limited to this example. It issufficient that the respects described later in (4. Layout ofinterconnection layer) below be reflected in the display device 1according to the present embodiment, and various known configurationsused in ordinary display devices may be used for the other respects.

For example, in the above-described configuration example, the pixelcircuit 210 includes four transistors, but a configuration of the pixelcircuit 210 is not limited to such an example. Another configurationexample of a pixel circuit applicable to the display device 1 is shownin FIG. 5. FIG. 5 is a schematic diagram showing another configurationexample of the pixel circuit according to the present embodiment.

Referring to FIG. 5, the pixel circuit 220 includes an organic lightemitting diode 221, five transistors 222, 223, 224, 225, and 226, andone holding capacitance 227. A configuration and operation of the pixelcircuit 220 are the same as a configuration and operation of a generalpixel circuit including five transistors, and thus a detaileddescription thereof will be omitted here. In this manner, in the presentembodiment, various known configurations may be applied as aconfiguration of a pixel circuit.

(4. Layout of Interconnection Layer)

Each of the above-described pixel circuits 210 and 220 is configured bystacking a plurality of interconnection layers (metal layers) havinginterconnections formed therein in an upper layer of a diffusion layerhaving transistors formed therein and further forming the organic lightemitting diode 211 in the upper layer thereof. A layout of aninterconnection layer in each of the pixel circuits 210 and 220 will bedescribed. Here, as an example, a layout of an interconnection layer inthe pixel circuit 220 shown in FIG. 5 will be described.

Note that, although the detailed description is omitted above, aninterconnection extending in the horizontal direction is connected to agate electrode of each transistor (transistors 222, 223, 225, and 226 inthe configuration example shown in FIG. 5) also in the pixel circuit220, similar to the pixel circuit 210. Although FIG. 5 shows only onepixel circuit 220, these interconnections are actually provided inrespective rows of a plurality of pixel circuits 220 arranged in amatrix. In the following description, interconnections provided toextend in the horizontal direction in response to respective rows of aplurality of pixel circuits 220 are also referred to as H scanninglines. As shown in FIG. 5, four H scanning lines 228 are present in onepixel circuit 220 (in FIG. 5, the H scanning lines 228 imitating theactual shapes in the interconnection layer are shown).

In addition, similarly to the pixel circuit 210, also in the pixelcircuit 220, interconnections (signal lines) extending in the verticaldirection for supplying a signal voltage corresponding to a video signaland the like are connected. Although only one pixel circuit 220 is shownin FIG. 5, the interconnections are actually provided for respectivecolumns of a plurality of pixel circuits 220 arranged in a matrix. Inthe following description, interconnections provided to extend in thevertical direction in response to respective columns of a plurality ofpixel circuits 220 are also referred to as V signal lines. As shown inFIG. 5, one V signal line 229 is present in one pixel circuit 220 (inFIG. 5, the V signal line 229 imitating the actual shape in theinterconnection layer is shown).

First, a stacked structure of the pixel circuit 220 will be describedwith reference to FIG. 6. FIG. 6 is a schematic cross-sectional viewshowing a stacked structure of the pixel circuit 220. In FIG. 6, astacked structure from a diffusion layer to an anode of the organiclight emitting diode 221 is schematically shown with respect to thepixel circuit 220.

Referring to FIG. 6, the pixel circuit 220 is configured with aplurality of interconnection layers 234, 237, and 240 formed in an upperlayer of the diffusion layer 231. In the diffusion layer 231,transistors (the transistors 222 to 226) are formed by forming activeregions functioning as a source region, a drain region, and a channelregion, a gate insulating film, a gate electrode, and the like on asemiconductor substrate such as Si. Note that, in FIG. 6, elements suchas transistors formed in the diffusion layer are not shown for the sakeof convenience.

An insulating layer 232 (hereinafter referred to as a first insulatinglayer 232) is stacked on the diffusion layer 231. The first insulatinglayer 232 is formed by stacking an insulator such a silicon oxide (SiO₂)to a prescribed thickness (the same applies to a second insulating layer235, a third insulating layer 238, and a fourth insulating layer 241which will be described later).

In the first insulating layer 232, a contact 233 for electricallyconnecting a region connected to an interconnection layer of an upperlayer such as each electrode (a source electrode, a drain electrode, anda gate electrode) of each transistor of the diffusion layer 231 and aninterconnection formed in the first interconnection layer 234 to bedescribed later in the upper layer is formed at a position correspondingto the region. The contact 233 is formed by forming a through hole(contact hole) in the first insulating layer 232 and then embedding aconductor such as tungsten (W) in the contact hole.

The interconnection layer 234 (hereinafter referred to as the firstinterconnection layer 234) is formed on the first insulating layer 232in which the contact 233 is formed. The first interconnection layer 234is formed by stacking a conductor such as aluminum (Al) to a prescribedthickness and then patterning the conductor film into a prescribed shape(the same applies to the second interconnection layer 237 and the thirdinterconnection layer 240 which will be described later).Interconnections (various interconnections including the H scanning line228 and the V signal line 229) shown in FIG. 5 are formed in the firstinterconnection layer 234, the second interconnection layer 237, and/orthe third interconnection layer 240.

The insulating layer 235 (hereinafter referred to as a second insulatinglayer 235) is formed on the first interconnection layer 234. A via 236(hereinafter referred to as a first via 236) for electrically connectinga corresponding interconnection formed in the first interconnectionlayer 234 of a lower layer and a corresponding interconnection formed inthe second interconnection layer 237 to be described later of an upperlayer to each other is formed in the second insulating layer 235. Thefirst via 236 is formed by forming a through hole (via hole) in thesecond insulating layer 235 and then embedding a conductor such as W inthe through hole (the same applies to a second via 239 and a third via242 to be described later).

The interconnection layer 237 (hereinafter referred to as a secondinterconnection layer 237) is formed on the second insulating layer 235having the first via 236 formed therein. The insulating layer 238(hereinafter referred to as a third insulating layer 238) is formed onthe second interconnection layer 237. A via 239 (hereinafter referred toas a second via 239) for electrically connecting a correspondinginterconnection formed in the second interconnection layer 237 of alower layer and the third interconnection layer 240 to be describedlater of an upper layer to each other is formed in the third insulatinglayer 238.

The interconnection layer 240 (hereinafter referred to as a thirdinterconnection layer 240) is formed on the third insulating layer 238having the second via 239 formed therein. The insulating layer 241(hereinafter referred to as a fourth insulating layer 241) is formed onthe third interconnection layer 240. A via 242 (hereinafter referred toas a third via 242) for electrically connecting a correspondinginterconnection formed in the third interconnection layer 240 of a lowerlayer and a corresponding interconnection formed in an anode 243 to bedescribed later of an upper layer to each other is formed in the fourthinsulating layer 241.

The pixel circuit 210 is manufactured by forming the organic lightemitting diode 211 on the fourth insulating layer 241 having the thirdvia 242 formed therein. Although FIG. 6 shows only the anode 243 of theorganic light emitting diode 211, the organic light emitting diode 211is formed by sequentially stacking an organic layer and a cathodefunctioning as a light emission layer on the anode 243.

Here, in the present embodiment, a capacitance element (the holdingcapacitance 227 shown in FIG. 5) is formed in the second interconnectionlayer 237 and the third interconnection layer 240. Specifically, a lowerelectrode (a capacitance element lower electrode 251) of the capacitanceelement is formed in the second interconnection layer 237. An upperelectrode (a capacitance element upper electrode 252) of the capacitanceelement is formed in the upper layer of the second interconnection layer237 through an insulator having a thickness corresponding to thecapacity of the capacitance element. The capacitance element upperelectrode 252 is provided inside the third insulating layer 238. Thatis, although the description is omitted above, the third insulatinglayer 238 is actually stacked in two stages with the capacitance elementupper electrode 252 as a boundary. After the second interconnectionlayer 237 is formed, an insulator having a thickness corresponding tothe capacity of the capacitance element is stacked, and the capacitanceelement upper electrode 252 is formed on the insulator by the samemethod as the interconnection layer. Thereafter, the third insulatinglayer 238 is formed by further stacking an insulator having a prescribedthickness.

In the third insulating layer 238, a second via 239 is also provided ata position corresponding to the capacitance element upper electrode 252.In addition, the capacitance element upper electrode 252 is electricallyconnected to an electrode 254 formed in the third interconnection layer240 through the second via 239. Since the electrode 254 is an electrodefor extracting the potential of the capacitance element upper electrode252 and is an electrode having the same potential as the capacitanceelement upper electrode 252, the electrode 254 will also be hereinafterreferred to as the capacitance element upper electrode 254.

Here, interconnections (that is, the H scanning line 228, the V signalline 229, and the like) included in the pixel circuit 210 and a specificlayout of a capacitance element (that is, the holding capacitance 227)will be examined. As described above, these interconnections are formedin the first interconnection layer 234, the second interconnection layer237, and/or the third interconnection layer 240. In addition, thecapacitance element lower electrode 251 and the capacitance elementupper electrode 254 of the capacitance element are respectively formedin the second interconnection layer 237 and the third interconnectionlayer 240. In this manner, the interconnections and the capacitanceelement lower electrode 251 and the capacitance element upper electrode254 of the capacitance element may be formed within the sameinterconnection layer.

Here, an attempt to reduce a pixel size for a reason such as an increasein definition of display in the display device 1 may result in variousproblems obstructing normal operation of the pixel circuit 220. Examplesof such problems include deterioration of emission luminance uniformitycaused by noise interference between electrodes due to an increase inparasitic capacitance between interconnections, deterioration ofluminance uniformity caused by deterioration of noise resistance due tothe pressure of the area of an electrode of a capacitance element, afailure of a short circuit between interconnections due to a pixelinterconnection becoming dense, a failure of interconnection open due tofilm skipping of an interconnection pattern having a small area, and thelike. Therefore, in a case in which a relatively small pixel size isparticularly required, it is important to devise layouts of the firstinterconnection layer 234, the second interconnection layer 237, and thethird interconnection layer 240 to prevent these problems from occurringto the utmost while keeping a pixel size small.

The inventors have, through ardent research, conceived preferred layoutsof the first interconnection layer 234, the second interconnection layer237, and the third interconnection layer 240 which are capable ofavoiding the above-described problems. Hereinafter, these preferredlayouts will be described in detail with reference to the accompanyingdrawings.

FIG. 7 is a diagram for describing an example of a layout of aninterconnection layer according to the present embodiment. In FIG. 7 andFIGS. 8 to 10 to be described later, layouts of the diffusion layer 231,the first interconnection layer 234, the second interconnection layer237, and the third interconnection layer 240 are schematically shown.

Note that, in FIG. 7 and FIGS. 8 to 10 to be described later, a layoutof an interconnection layer is described, and thus only a layout of thecontact 233 is shown with respect to the diffusion layer 231. Inaddition, a connection state between interconnection layers is shownwith respect to the first interconnection layer 234, the secondinterconnection layer 237, and the third interconnection layer 240, andthus layouts of the first via 236, the second via 239, and the third via242 are also shown together with layouts of interconnections within theinterconnection layers.

Further, in FIG. 7 and FIGS. 8 to 10 to be described later, a contactand a via with “a” at the end of a reference numeral represent a contactand a via which are ultimately connected to the anode 243 in the upperlayer. Similarly, a contact and a via with “b” at the end of a referencenumeral represent a contact and a via which are ultimately connected tothe capacitance element lower electrode 251 in the upper layer.Similarly, a contact and a via with “c” at the end of a referencenumeral represent a contact and a via which are ultimately connected tothe V signal line 229 in the upper layer. Similarly, a contact and a viawith “d” at the end of a reference numeral represent a contact and a viawhich are ultimately connected to the H scanning line 228 in the upperlayer.

Further, in FIG. 7 and FIGS. 8 to 10 to be described later, for the sakeof description, an interconnection related to the anode 243 (that is, aninterconnection having the same potential as the anode 243) is indicatedby a dashed line, an interconnection related to the capacitance elementlower electrode 251 (that is, the capacitance element lower electrode251 itself and an interconnection having the same potential as thecapacitance element lower electrode 251) is indicated by a thick solidline, an interconnection related to the V signal line 229 (that is, theV signal line 229 itself and an interconnection having the samepotential as the V signal line 229) is indicated by an alternatingdotted-dashed line, and an interconnection related to the H scanningline 228 (that is, the H scanning line 228 itself and an interconnectionhaving the same potential as the H scanning line 228) is indicated by athin solid line with respect to the first interconnection layer 234, thesecond interconnection layer 237, and the third interconnection layer240.

FIG. 7 shows an example of a layout in a case in which the H scanningline 228 and the V signal line 229 are formed in the firstinterconnection layer 234 and the second interconnection layer 237. Asshown in FIG. 7, in the present embodiment, one of the H scanning line228 and the V signal line 229, provided for one pixel circuit 220, whichis larger in number is formed in a lower-level layer. In a case of aconfiguration example of the pixel circuit 220 shown in FIG. 5, thenumber of H scanning lines 228 provided for one pixel circuit 220 islarger than the number of V signal lines 229 as described above.Therefore, as shown in the drawing, in a case in which the H scanningline 228 and the V signal line 229 are formed in the firstinterconnection layer 234 and the second interconnection layer 237, theH scanning line 228 is formed in the first interconnection layer 234 andthe V signal line 229 is formed in the second interconnection layer 237.

In this case, as shown in FIG. 7, in the first interconnection layer234, an interconnection (an interconnection indicated by a dashed linein the drawing, and hereinafter, also referred to as a connectioninterconnection related to the anode 243) for connecting a correspondingelectrode of the diffusion layer 231 to the anode 243 formed in theupper layer of the third interconnection layer 240, an interconnection(an interconnection indicated by a thick solid line in the drawing, andhereinafter, also referred to as a connection interconnection related tothe capacitance element) for connecting a corresponding electrode of thediffusion layer 231 to the capacitance element lower electrode 251formed in the second interconnection layer 237, and an interconnection(an interconnection indicated by an alternating dotted-dashed line inthe drawing, and hereinafter, also referred to as a connectioninterconnection related to the V signal line 229) for connecting acorresponding electrode of the diffusion layer 231 to the V signal line229 formed in the second interconnection layer 237 are formed togetherwith the H scanning lines 228. Further, in the second interconnectionlayer 237, the capacitance element lower electrode 251 and a connectioninterconnection related to the anode 243 are formed together with the Vsignal line 229. Further, in the third interconnection layer 240, thecapacitance element upper electrode 254 and a connection interconnectionrelated to the anode 243 are formed. Note that the number of each ofconnection interconnections related to the anode 243, connectioninterconnections related to the capacitance element, and connectioninterconnections related to the V signal line 229, which are to beformed in each interconnection layer, is one.

Here, for comparison, FIG. 8 shows an example of a layout of aninterconnection layer different from that in the present embodiment in acase in which the H scanning line 228 and the V signal line 229 areformed in the first interconnection layer 234 and the secondinterconnection layer 237. FIG. 8 is a diagram for comparison with thelayout shown in FIG. 7, and is a diagram showing an example of a layoutin a case in which the H scanning line 228 and the V signal line 229 areformed in an interconnection layer different from that in the presentembodiment in a case in which the H scanning line 228 and the V signalline 229 are formed in the first interconnection layer 234 and thesecond interconnection layer 237. As shown in FIG. 8, contrary to thelayout according to the present embodiment shown in FIG. 7, it isassumed that, one of the H scanning line 228 and the V signal line 229,provided for one pixel circuit 220, which is larger in number is formedin a higher-level layer. That is, it is assumed that the V signal line229 is formed in the first interconnection layer 234, and the H scanningline 228 is formed in the second interconnection layer 237.

In this case, as shown in FIG. 8, in the first interconnection layer234, a connection interconnection related to the anode 243, a connectioninterconnection related to the capacitance element, and aninterconnection (an interconnection indicated by a thin solid in thedrawing, and hereinafter, also referred to as a connectioninterconnection related to the H scanning line 228) for connecting acorresponding electrode of the diffusion layer 231 to the H scanningline 228 formed in the second interconnection layer 237 are formedtogether with the V signal line 229. The number of connectioninterconnections related to the H scanning line 228 corresponding to thenumber of H scanning lines 228 are formed. Further, in the secondinterconnection layer 237, the capacitance element lower electrode 251and a connection interconnection related to the anode 243 are formedtogether with a larger number of H scanning lines 228. Further, in thethird interconnection layer 240, the capacitance element upper electrode254 and a connection interconnection related to the anode 243 areformed.

Comparing the layout according to the present embodiment shown in FIG. 7and the layout shown in FIG. 8 with each other, the H scanning lines 228which are a larger number of interconnections are formed in the firstinterconnection layer 234 which is a lower-level layer in the layoutaccording to the present embodiment, and thus an interconnection patternof the first interconnection layer 234 becomes relatively dense. On theother hand, in the layout shown in FIG. 8, the H scanning lines 228which are a larger number of interconnections are not formed in thefirst interconnection layer 234, but it is necessary to form the numberof connection interconnections related to the H scanning line 228corresponding to the number of H scanning lines 228 in the firstinterconnection layer 234. Therefore, it can be said that the area ofthe connection interconnection related to the H scanning line 228 issmaller than that of the H scanning line 228, and consequently, thedensity of an interconnection pattern in the first interconnection layer234 is not greatly lower than that of the layout according to thepresent embodiment.

On the other hand, in the layout according to the present embodiment,the V signal lines 229 which are a smaller number of interconnectionsare formed in the second interconnection layer 237, and thus aninterconnection pattern of the second interconnection layer 237 becomesrelatively sparse. On the other hand, in the layout shown in FIG. 8, theH scanning lines 228 which are a larger number of interconnections areformed in the second interconnection layer 237, and thus aninterconnection pattern of the second interconnection layer 237 becomesrelatively dense.

In this manner, according to the present embodiment, with respect to theH scanning line 228 and the V signal line 229, it is possible to make aninterconnection pattern in the second interconnection layer 237 which isa higher-level layer more sparse by configuring layouts of the firstinterconnection layer 234 and the second interconnection layer 237 so asto form the H scanning lines 228 which are a larger number ofinterconnections provided for one pixel circuit 220 in the firstinterconnection layer 234 which is a lower-level layer.

The interconnection pattern in the second interconnection layer 237becomes more sparse, and thus it is possible to suppress the occurrenceof deterioration of luminance uniformity caused by an increase inparasitic capacitance between interconnections in the secondinterconnection layer 237, a failure of a short circuit betweeninterconnections, and the like which are described above. Further, inthe present embodiment, since the capacitance element lower electrode251 is provided in the second interconnection layer 237, theinterconnection pattern of the second interconnection layer 237 becomessparse, and thus the degree of freedom of the layout of the capacitanceelement lower electrode 251 increases and it is possible to secure asufficient area in which desired capacity can be realized with respectto the capacitance element lower electrode 251. Therefore, it ispossible to suppress the occurrence of deterioration of luminanceuniformity caused by the pressure of an area of an electrode of thecapacitance element, a failure of interconnection open due to aninterconnection pattern (electrode) having a small area not beingprovided, and the like. Accordingly, it is possible to suppress theoccurrence of these various problems and to realize the display device 1with higher reliability and higher definition.

Here, FIG. 7 shows an example of a layout in a case in which the Hscanning line 228 and the V signal line 229 are respectively formed inthe first interconnection layer 234 and the second interconnection layer237, but the present embodiment is not limited to such an example. Alayout method (that is, a method of forming one of the H scanning line228 and the V signal line 229, provided for one pixel circuit 220, whichis larger in number in a lower-level layer) can be applied even in acase in which the H scanning line 228 and the V signal line 229 areformed in other interconnection layers.

Another example of a layout of an interconnection layer according to thepresent embodiment will be described with reference to FIG. 9. FIG. 9 isa diagram for describing another example of a layout of aninterconnection layer according to the present embodiment.

FIG. 9 shows an example of a layout in a case in which the H scanningline 228 and the V signal line 229 are formed in the firstinterconnection layer 234, the second interconnection layer 237, and thethird interconnection layer 240. As shown in FIG. 9, even in such acase, in the present embodiment, one of the H scanning line 228 and theV signal line 229, provided for one pixel circuit 220, which is largerin number than the other is formed in a lower-level layer. Therefore,for example, as shown in the drawing, the H scanning line 228 is formedin the first interconnection layer 234 and the second interconnectionlayer 237, and the V signal line 229 is formed in the thirdinterconnection layer 240.

In this case, as shown in FIG. 9, for example, in the firstinterconnection layer 234, a connection interconnection related to theanode 243, a connection interconnection related to the capacitanceelement, and a connection interconnection related to the V signal line229 are formed together with some (three H scanning lines in the exampleshown in the drawing) of the H scanning lines 228. Further, in thesecond interconnection layer 237, the capacitance element lowerelectrode 251, a connection interconnection related to the anode 243,and a connection interconnection related to the V signal line 229 areformed together with the remaining H scanning lines 228 (one H scanningline in the example shown in the drawing). Further, in the thirdinterconnection layer 240, the capacitance element upper electrode 254and a connection interconnection related to the anode 243 are formedtogether with the V signal line 229. In the example shown in FIG. 7, theplurality of H scanning lines 228 are formed in the same interconnectionlayer, but the plurality of H scanning lines 228 may be formed so as tobe dispersed to different interconnection layers in this manner in thepresent embodiment.

Here, for comparison, FIG. 10 shows an example of a layout of aninterconnection layer different from that in the present embodiment in acase in which the H scanning line 228 and the V signal line 229 areformed in the first interconnection layer 234, the secondinterconnection layer 237, and the third interconnection layer 240. FIG.10 is a diagram for comparison with the layout shown in FIG. 9, and is adiagram showing an example of a layout in a case in which the H scanningline 228 and the V signal line 229 are formed in an interconnectionlayer different from that in the present embodiment in a case in whichthe H scanning line 228 and the V signal line 229 are formed in thefirst interconnection layer 234, the second interconnection layer 237,and the third interconnection layer 240. As shown in FIG. 10, contraryto the layout according to the present embodiment shown in FIG. 9, it isassumed that one of the H scanning line 228 and the V signal line 229,provided for one pixel circuit 220, which is larger in number is formedin a higher-level layer. Here, it is assumed that the V signal line 229is formed in the first interconnection layer 234, and the H scanningline 228 is formed in the third interconnection layer 240.

In this case, as shown in FIG. 10, in the first interconnection layer234, a connection interconnection related to the anode 243, a connectioninterconnection related to the capacitance element, and a connectioninterconnection related to the H scanning line 228 are formed togetherwith the V signal line 229. Further, in the second interconnection layer237, a connection interconnection related to the anode 243 and aconnection interconnection related to the H scanning line 228 are formedtogether with the capacitance element lower electrode 251. Note that, inthe first interconnection layer 234 and the second interconnection layer237, the number of connection interconnections related to the H scanningline 228 corresponding to the number of H scanning lines 228 are formed.Further, in the third interconnection layer 240, the capacitance elementupper electrode 254 and a connection interconnection related to theanode 243 are formed together with a larger number of H scanning lines228.

Comparing the layout according to the present embodiment shown in FIG. 9and the layout shown in FIG. 10 with each other, half of the H scanninglines 228 which are a larger number of interconnections are formed inthe first interconnection layer 234 which is a lower-level layer in thelayout according to the present embodiment, and thus an interconnectionpattern of the first interconnection layer 234 becomes relatively dense.On the other hand, in the layout shown in FIG. 8, the H scanning lines228 which are a larger number of interconnections are not formed in thefirst interconnection layer 234, but it is necessary to form the numberof connection interconnections related to the H scanning line 228corresponding to the number of H scanning lines 228 in the firstinterconnection layer 234. Therefore, it can be said that the area ofthe connection interconnection related to the H scanning line 228 issmaller than that of the H scanning line 228, and consequently, thedensity of an interconnection pattern in the first interconnection layer234 is not greatly lower than that of the layout according to thepresent embodiment.

On the other hand, in the layout according to the present embodiment,the V signal lines 229 which are a smaller number of interconnectionsare formed in the third interconnection layer 240, and thusinterconnection patterns of the second interconnection layer 237 and thethird interconnection layer 240 become relatively sparse. On the otherhand, in the layout shown in FIG. 8, since the H scanning lines 228which are a larger number of interconnections are formed in the thirdinterconnection layer 240, it is necessary to form the number ofconnection interconnections related to the H scanning line 228corresponding to the number of H scanning lines 228 in the secondinterconnection layer 237, and thus an interconnection pattern of thesecond interconnection layer 237 becomes relatively dense.

In this manner, according to the layout shown in FIG. 9, with respect tothe H scanning line 228 and the V signal line 229, it is possible tomake interconnection patterns in the second interconnection layer 237and the third interconnection layer 240 which are higher-level layersmore sparse by configuring layouts of the first interconnection layer234, the second interconnection layer 237, and the third interconnectionlayer 240 so as to form the H scanning lines 228 which are a largernumber of interconnections provided for one pixel circuit 220 in thefirst interconnection layer 234 and the second interconnection layer 237which are lower-level layers. Therefore, it is possible to the sameeffects as those in a case in which the above-described layout shown inFIG. 7 is applied, that is, to realize the display device 1 with highdefinition and higher reliability.

Further, according to the present embodiment, it is also possible toexhibit the following effects.

For example, in a case in which it is not possible to secure asufficient area in which desired capacity can be realized in the secondinterconnection layer 237 with respect to the capacitance element lowerelectrode 251 by performing the layouts as shown in FIGS. 8 and 10, itmay be necessary to increase the number of interconnection layers inorder to create a capacitance element having desired capacity and toform capacitance elements in the increased interconnection layers. Inthis case, the number of masks and the number of steps are increased dueto the increase in the number of interconnection layers, which mayincrease manufacturing costs. On the other hand, according to the layoutof the present embodiment, since it is possible to secure a sufficientarea of the capacitance element lower electrode 251 as described above,it is possible to form a capacitance element with desired capacitywithout causing such an increase in the number of interconnectionlayers. In this manner, according to the present embodiment, it is alsopossible to exhibit an effect of suppressing an increase inmanufacturing costs.

Further, in the present embodiment, a larger number of interconnectionsare formed in an interconnection layer of a lower layer, and thus aninterconnection pattern of the interconnection layer of a lower layerbecomes dense to no small extent, as compared to a case in which alarger number of interconnections are formed in an interconnection layerof an upper layer and an isolated connection interconnection (theabove-described connection interconnection related to the H scanningline 228, and the like) is formed in an interconnection layer of a lowerlayer. In this manner, an interconnection pattern in an interconnectionlayer of a lower layer closer to the diffusion layer 231 havingtransistors formed therein becomes dense, and thus it is possible toimprove an effect of shielding the transistors from light. Therefore, itis possible to more suppress a fluctuation in characteristics of thetransistors due to exposure to light and to further improve reliabilityof the display device 1.

In addition, an interconnection pattern in an interconnection layer ofan upper layer, particularly, a highest-level interconnection layer canbe made relatively sparse, and thus it is possible to improve flatnessof the anode 243 of the organic light emitting diode 221 formed in theupper layer located at a higher position of the highest-levelinterconnection layer. Thereby, it is possible to improve light emissionefficiency of the organic light emitting diode 221, and a furtherimprovement in display quality can be realized.

In addition, an interconnection pattern of an interconnection layer ofan upper layer can be made relatively sparse, and thus the degree offreedom of arrangement of a connection interconnection related to theanode 243 formed in the third interconnection layer 240 which is ahighest-level interconnection layer (that is, arrangement of the thirdvia 242 for connecting the connection interconnection related to theanode 243 and the anode 243 in the upper layer to each other) isimproved. Thereby, the design of layouts of pixels is more facilitated.

This point will be described in more detail with reference to FIGS. 11and 12. FIG. 11 is a diagram showing an example of arrangement of thethird vias 242 in three sub-pixels in a case in which one pixel isformed of these three sub-pixels. FIG. 12 is a diagram showing anexample of arrangement of the third vias 242 in four sub-pixels in acase in which one pixel is formed of these four sub-pixels.

Both FIGS. 11 and 12 show a top view having a configuration in which theanode 243 and an organic layer 261 (a layer functioning as a lightemission layer in the light emitting organic light emitting diode 221)corresponding to one pixel are stacked on the left side of the drawing,and simulatively shows arrangement of the third vias 242 for such aconfiguration. In addition, the right side of the drawing shows a topview of a configuration 262 in which the diffusion layer 231 andinterconnection layers (the first interconnection layer 234, the secondinterconnection layer 237, and the third interconnection layer 240) arestacked, similarly corresponding to one pixel, and simulatively showsarrangement of the third vias 242 for such a configuration. Regardingthe configuration 262 in which the diffusion layer 231 and theinterconnection layers are stacked, detailed illustration of the insideof each layer is omitted for the sake of convenience. Note that, inFIGS. 11 and 12, regarding the organic layer 261 and the configuration262 in which the diffusion layer 231 and the interconnection layers arestacked, a letter indicating the color of its corresponding sub-pixel(R: Red, G: Green, B: Blue, W: White) is attached to the end of areference numeral. Actually, since the color of each sub-pixel iscontrolled by a color filter (CF) provided at a higher-level layer thanthe organic light emitting diode 221, there is no difference instructure due to color with regard to the organic layer 261 and theconfiguration 262 in which the diffusion layer 231 and theinterconnection layer are stacked.

As shown in FIG. 11, in a case in which one pixel is formed of threesub-pixels, the arrangement of the third vias 242 is substantially thesame in the sub-pixels. Therefore, there is not much advantage due to animprovement in the degree of freedom of arrangement of the third vias242.

On the other hand, as shown in FIG. 12, in a case in which one pixel isformed of four sub-pixels, there is a difference in the arrangement ofthe third vias 242 between the sub-pixels. That is, it is also necessaryto change arrangement of a connection interconnection related to theanode 243 in the third interconnection layer 240 for each sub-pixel. Inthis case, for example, as a result of the execution of the layout asshown in FIG. 10, when an interconnection pattern in the thirdinterconnection layer 240 is dense, the degree of freedom of arrangementof the connection interconnection related to the anode 243 is low.Therefore, in order to make arrangement of the connectioninterconnection related to the anode 243 different for each sub-pixel,there is a concern that it is necessary to make the entire layout of thethird interconnection layer 240 different for each sub-pixel. In thiscase, accordingly, it may also be necessary to make layouts of thesecond interconnection layer 237 and the first interconnection layer 234of lower layers different for each sub-pixel, which results in anenormous amount of work for the layouts and a heavy burden on adesigner.

On the other hand, according to the present embodiment, it is possibleto make an interconnection pattern of an interconnection layer of anupper layer relatively sparse, and thus the degree of freedom ofarrangement of a connection interconnection related to the anode 243 inthe third interconnection layer 240 is high. Therefore, it is possibleto configure a layout of the third interconnection layer 240 so thatonly the arrangement of the connection interconnection related to theanode 243 is different for each sub-pixel and arrangements of the otherinterconnections are the same for each sub-pixel. In this case, withregard to the layouts of the second interconnection layer 237 and thefirst interconnection layer 234 of lower layers, it is sufficient ifonly arrangement of a connection interconnection related to the anode243 is made different for each sub-pixel, and thus the degree ofdifficulty in designing the layouts is lowered. In this manner, a layoutmethod for an interconnection layer according to the present embodimentalso has an effect of reducing the degree of difficulty in designing alayout of one pixel in a case in which arrangement of the third via 242(that is, a via for connecting a highest-level interconnection layer andthe anode 243 to each other) is different for each sub-pixel as in acase in which the pixel is formed of four sub-pixels.

A layout of an interconnection layer according to the present embodimenthas been described above. Note that, although only two examples oflayouts shown in FIGS. 7 and 9 have been taken above, it is possible toapply a layout method for an interconnection layer according to thepresent embodiment even in a case in which the number of interconnectionlayers is different from three layers illustrated in the abovedescription (for example, a case in which the number of interconnectionlayers is four or more), a case in which arrangement positions of the Hscanning line 228 and the V signal line 229 in the interconnectionlayers are different from each other, a case in which the number of Hscanning lines 228 and the number of V signal lines 229 are differentfrom each other (for example, a case in which both the numbers areplural), a case in which magnitude relations of the number of H scanninglines 228 and the number of V signal lines 229 provided for each of thepixel circuits 210 and 220 are inverse, and the like. The layout methodfor the interconnection layer according to the present embodiment can beapplied to various display devices as long as the display devices aredisplay devices driven by an active matrix method. The number ofconnection interconnections related to the H scanning line 228 or thenumber of connection interconnections related to the V signal lines 229in a lower-level interconnection layer is reduced by applying the layoutmethod for the interconnection layer according to the present embodimentregardless of the number of interconnection layers and the like, andconsequently, it is possible to make an interconnection pattern of ahigher-level interconnection layer relatively sparse. In addition, it ispossible to sufficiently secure the area of an electrode of acapacitance element by providing the electrode of the capacitanceelement (the capacitance element lower electrode 251 and/or thecapacitance element upper electrode 254 in the interconnection layerhaving a relatively sparse interconnection pattern. Therefore, similarlyto the above-described embodiment, it is possible to obtain variouseffects such as an improvement in reliability.

(5. Specific Configuration Example of Display Device)

A more specific configuration example of the display device 1 accordingto the present embodiment described hereinabove will now be described.FIG. 13 is a cross-sectional view showing a specific configurationexample of the display device 1 according to the present embodiment.FIG. 13 shows a partial cross-sectional view of the display device 1.

Referring to FIG. 13, the display device 1 according to the presentembodiment includes, on a first substrate 11, a plurality of organiclight emitting diodes 211 each of which is a light emitting element thatemits white light and a CF layer 33 that is provided on the organiclight emitting diodes 211 and in which CFs of some colors are formed tocorrespond to the organic light emitting diodes 211. Further, a secondsubstrate 34 that contains a material transparent to light from theorganic light emitting diode 211 is placed on the CF layer 33. Further,on the first substrate 11, thin film transistors (TFTs) 15 for drivingthe organic light emitting diode 211 are provided to correspond to eachof the organic light emitting diodes 211. The TFT 15 corresponds to eachof the transistors included in the pixel circuit 210 described above(the driving transistor 212, the sampling transistor 213, the lightemission control transistor 214, and the switching transistor 217). Anarbitrary organic light emitting diode 211 is selectively driven by theTFTs 15; light from the driven organic light emitting diode 211 passesthrough the corresponding CF and the color of the light is converted asappropriate; and the light is emitted from the upper side via the secondsubstrate 34; thereby, a desired image, a desired character, etc. aredisplayed.

Note that, in the following description, the stacking direction of thelayers in the display device 1 is referred to also as an up and downdirection. In this event, the side on which the first substrate 11 isplaced is defined as a down side, and the side on which the secondsubstrate 34 is placed is defined as an up side. Further, a planeperpendicular to the up and down direction is referred to also as ahorizontal plane.

Thus, the display device 1 shown in FIG. 13 is a top emission displaydevice capable of color display that is driven by an active matrixsystem. However, the present embodiment is not limited to this example,and the display device 1 according to the present embodiment may be abottom emission display device that emits light via the first substrate11.

(First Substrate and Second Substrate)

In the illustrated configuration example, the first substrate 11includes a Si substrate. Further, the second substrate 34 containsquartz glass. However, the present embodiment is not limited to thisexample, and various known materials may be used as the first substrate11 and the second substrate 34. For example, each of the first substrate11 and the second substrate 34 may include a high strain point glasssubstrate, a soda-lime glass (a mixture of Na₂O, CaO, and SiO₂)substrate, a borosilicate glass (a mixture of Na₂O, B₂O₃, and SiO₂)substrate, a forsterite (Mg₂SiO₄) substrate, a lead glass (a mixture ofNa₂O, PbO, and SiO₂) substrate, various glass substrates in which aninsulating film is formed on a surface, a quartz substrate, a quartzsubstrate in which an insulating film is formed on a surface, a Sisubstrate in which an insulating film is formed on a surface, or anorganic polymer substrate (for example, polymethyl methacrylate (PMMA),polyvinyl alcohol (PVA), polyvinylphenol (PVP), a polyether sulfone(PES), a polyimide, a polycarbonate, polyethylene terephthalate (PET),or the like). The materials contained in the first substrate 11 and thesecond substrate 34 may be the same, or may be different. However, sincethe display device 1 is of the top emission type as described above, thesecond substrate 34 preferably contains a material with a hightransmittance that can transmit the light from the organic lightemitting diode 211 favorably.

(Light Emitting Element and Second Member)

The organic light emitting diode 211 includes a first electrode 21, anorganic layer 23 provided on the first electrode 21, and a secondelectrode 22 formed on the organic layer 23. More specifically, a secondmember 52 in which openings 25 are provided so as to expose at leastparts of the first electrode 21 is stacked on the first electrode 21,and the organic layer 23 is provided on portions of the first electrode21 that are exposed at the bottoms of the openings 25. That is, theorganic light emitting diode 211 has a configuration in which the firstelectrode 21, the organic layer 23, and the second electrode 22 arestacked in this order in the opening 25 of the second member 52. Thisstacked structure functions as a luminescence section 24 of each pixel.That is, a portion of the organic light emitting diode 211 falling underthe opening 25 of the second member 52 serves as a luminescence surface.Further, the second member 52 functions as a pixel defining film that isprovided between pixels and partitions the area of the pixel.

The organic layer 23 includes a luminescence layer containing an organicluminescent material, and can emit white light. The specificconfiguration of the organic layer 23 is not limited, and may be variouspublicly known configurations. For example, the organic layer 23 mayhave a stacked structure of a hole transport layer, a luminescencelayer, and an electronic transport layer, a stacked structure of a holetransport layer and a luminescence layer that serves also as anelectronic transport layer, a stacked structure of a hole injectionlayer, a hole transport layer, a luminescence layer, an electronictransport layer, and an electron injection layer, or the like. Further,in a case where each of these stacked structures or the like is used asa “tandem unit,” the organic layer 23 may have a tandem structure of twostages in which a first tandem unit, a connection layer, and a secondtandem unit are stacked. Alternatively, the organic layer 23 may have atandem structure of three or more stages in which three or more tandemunits are stacked. In a case where the organic layer 23 includes aplurality of tandem units, an organic layer 23 that emits white light asa whole can be obtained by assigning red, green, and blue to theluminescent colors of the luminescence layers of the tandem units.

In the illustrated configuration example, the organic layer 23 is formedby depositing an organic material by vacuum vapor deposition. However,the present embodiment is not limited to this example, and the organiclayer 23 may be formed by various publicly known methods. For example,as the method for forming the organic layer 23, physical vapordeposition methods (PVD methods) such as the vacuum vapor depositionmethod, printing methods such as the screen printing method and theinkjet printing method, a laser transfer method in which a stackedstructure of a laser absorbing layer and an organic layer formed on asubstrate for transfer is irradiated with laser light to separate theorganic layer on the laser absorbing layer and the organic layer istransferred, various application methods, etc. may be used.

The first electrode 21 functions as an anode. That is, the firstelectrode 21 corresponds to the anode 243 shown in FIG. 6 above. Sincethe display device 1 is of the top emission type as described above, thefirst electrode 21 contains a material capable of reflecting the lightfrom the organic layer 23. In the illustrated configuration example, thefirst electrode 21 contains an alloy of aluminum and neodymium (Al—Ndalloy). Further, the film thickness of the first electrode 21 isapproximately 0.1 μm to 1 μm, for example. However, the presentembodiment is not limited to this example, and the first electrode 21may contain various publicly known materials used as the material of anelectrode on the light reflection side that functions as an anode in acommon organic EL display device. Further, the film thickness of thefirst electrode 21 is not limited to the above example either, and thefirst electrode 21 may be formed in film thickness ranges commonlyemployed in organic EL display devices, as appropriate.

For example, the first electrode 21 may contain a metal with a high workfunction, such as platinum (Pt), gold (Au), silver (Ag), chromium (Cr),tungsten (W), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), ortantalum (Ta), or an alloy with a high work function (for example, aAg—Pd—Cu alloy containing silver as a main component and containing 0.3mass % to 1 mass % of palladium (Pd) and 0.3 mass % to 1 mass % ofcopper, an Al—Nd alloy, or the like). Alternatively, the first electrode21 may contain an electrically conductive material having a small workfunction value and a high light reflectance, such as aluminum or analloy containing aluminum. In this case, it is preferable to improvehole injection properties by providing an appropriate hole injectionlayer on the first electrode 21, or the like. Alternatively, the firstelectrode 21 may have a structure in which a transparent electricallyconductive material excellent in hole injection characteristics, such asan oxide of indium and tin (ITO) or an oxide of indium and zinc (IZO),is stacked on a reflective film with high light reflectivity such as adielectric multiple-layer film or aluminum.

The second electrode 22 functions as a cathode. Since the display device1 is of the top emission type as described above, the second electrode22 contains a material capable of transmitting the light from theorganic layer 23. In the illustrated configuration example, the secondelectrode 22 contains an alloy of magnesium and silver (Mg—Ag alloy).Further, the film thickness of the second electrode 22 is approximately10 nm, for example. However, the present embodiment is not limited tothis example, and the second electrode 22 may contain various publiclyknown materials used as the material of an electrode on the lighttransmission side that functions as a cathode in a common organic ELdisplay device. Further, the film thickness of the second electrode 22is not limited to the above example either, and the second electrode 22may be formed in film thickness ranges commonly employed in organic ELdisplay devices, as appropriate.

For example, the second electrode 22 may contain aluminum, silver,magnesium, calcium (Ca), sodium (Na), strontium (Sr), an alloy of analkali metal and silver, an alloy of an alkaline earth metal and silver(for example, an alloy of magnesium and silver (Mg—Ag alloy)), an alloyof magnesium and calcium (Mg—Ca alloy), an alloy of aluminum and lithium(Al—Li alloy), or the like. In a case where each of these materials isused in a single layer, the film thickness of the second electrode 22 isapproximately 4 nm to 50 nm, for example. Alternatively, the secondelectrode 22 may have a structure in which a layer of any of thematerials described above and a transparent electrode containing, forexample, ITO or IZO (with a thickness of, for example, approximately 30nm to 1 μm) are stacked from the organic layer 23 side. In a case wheresuch a stacked structure is used, the thickness of the layer of any ofthe materials described above may be as thin as approximately 1 nm to 4nm, for example. Alternatively, the second electrode 22 may include onlya transparent electrode. Alternatively, the second electrode 22 may beprovided with a bus electrode (auxiliary electrode) containing a lowresistance material, such as aluminum, an aluminum alloy, silver, asilver alloy, copper, a copper alloy, gold, or a gold alloy, to reducethe resistance of the second electrode 22 as a whole.

In the illustrated configuration example, each of the first electrode 21and the second electrode 22 is formed by forming a material as a filmwith a prescribed thickness by the vacuum vapor deposition method andthen patterning the film by the etching method. However, the presentembodiment is not limited to this example, and the first electrode 21and the second electrode 22 may be formed by various publicly knownmethods. Examples of the method for forming the first electrode 21 andthe second electrode 22 include vapor deposition methods including theelectron beam vapor deposition method, the hot filament vapor depositionmethod, and the vacuum vapor deposition method, the sputtering method,the chemical vapor deposition method (CVD method), the metal organicchemical vapor deposition method (MOCVD method), a combination of theion plating method and the etching method, various printing methods (forexample, the screen printing method, the inkjet printing method, themetal mask printing method, etc.), plating methods (the electroplatingmethod, the electroless plating method, etc.), the lift-off method, thelaser ablation method, the sol-gel method, etc.

The second member 52 is formed by forming SiO₂ as a film with aprescribed film thickness by the CVD method and then patterning the SiO₂film using photolithography technology and etching technology. However,the material of the second member 52 is not limited to this example, andvarious materials having insulating properties may be used as thematerial of the second member 52. Examples of the material contained inthe second member 52 include SiO₂, MgF, LiF, a polyimide resin, anacrylic resin, a fluorine resin, a silicone resin, a fluorine-basedpolymer, a silicone-based polymer, etc. However, as described later, thesecond member 52 contains a material having a lower refractive indexthan the material of a first member 51.

(Configuration of Parts Below Light Emitting Element)

On the first substrate 11, the first electrode 21 included in theorganic light emitting diode 211 is provided on an interlayer insulatinglayer 16 containing SiON. Then, the interlayer insulating layer 16covers a light emitting element driving section formed on the firstsubstrate 11.

The light emitting element driving section includes a plurality of TFTs15. In other words, the light emitting element driving sectioncorresponds to a driving circuit of the pixel circuit 210. The TFT 15includes a gate electrode 12 formed on the first substrate 11, a gateinsulating film 13 formed on the first substrate 11 and the gateelectrode 12, and a semiconductor layer 14 formed on the gate insulatingfilm 13. A region of the semiconductor layer 14 located immediatelyabove the gate electrode 12 functions as a channel region 14A, andregions located so as to sandwich the channel region 14A function assource/drain regions 14B. Note that, although in the illustrated examplethe TFT 15 is of a bottom gate type, the present embodiment is notlimited to this example, and the TFT 15 may be of a top gate type.

An interlayer insulating layer 16 including two layers (a lower layerinterlayer insulating layer 16A and an upper layer interlayer insulatinglayer 16B) is stacked on the semiconductor layer 14 by the CVD method.In this event, after the lower layer interlayer insulating layer 16A isstacked, contact holes 17 are provided in portions of the lower layerinterlayer insulating layer 16A corresponding to the source/drainregions 14B so as to expose the source/drain regions 14B, by usingphotolithography technology and etching technology, for example, and aninterconnection 18 containing aluminum is formed so as to fill thecontact hole 17. The interconnections 18 are formed by combining thevacuum vapor deposition method and the etching method, for example.After that, the upper layer interlayer insulating layer 16B is stacked.

In a portion of the upper layer interlayer insulating layer 16B wherethe interconnection 18 is provided, a contact hole 19 is provided so asto expose the interconnection 18, by using photolithography technologyand etching technology, for example. Then, when forming the firstelectrode 21 of the organic light emitting diode 211, the firstelectrode 21 is formed so as to be in contact with the interconnection18 via the contact hole 19. Thus, the first electrode 21 of the organiclight emitting diode 211 is electrically connected to a source/drainregion 14B of a TFT 15 (in the example of the pixel circuit shown inFIG. 3, corresponding to the drain region of the driving transistor 212)via the interconnection 18.

Note that, although in the above example the interlayer insulating layer16 contains SiON, the present embodiment is not limited to this example.The interlayer insulating layer 16 may contain various publicly knownmaterials that can be used as an interlayer insulating layer in a commonorganic EL display device. For example, as the material contained in theinterlayer insulating layer 16, SiO₂-based materials (for example, SiO₂,BPSG, PSG, BSG, AsSG, PbSG, SiON, spin-on glass (SOG), low melting pointglass, a glass paste, and the like), SiN-based materials, and insulatingresins (for example, a polyimide resin, a novolac-based resin, anacrylic-based resin, polybenzoxazole, and the like) may be used singlyor in combination, as appropriate. Further, the method for forming theinterlayer insulating layer 16 is not limited to the above exampleeither, and publicly known methods such as the CVD method, theapplication method, the sputtering method, and various printing methodsmay be used for the formation of the interlayer insulating layer 16.Furthermore, although in the above example the interconnection 18 isformed by forming aluminum as a film and patterning the film by thevacuum vapor deposition method and the etching method, the presentembodiment is not limited to this example. The interconnection 18 may beformed by forming, as a film, any of various materials that are used asan interconnection in a common organic EL display device and patterningthe film by various methods.

Further, FIG. 13 shows only one interconnection layer for the sake ofconvenience. Actually, as described above with reference to FIG. 6, aplurality of interconnection layers may be formed on a diffusion layerhaving the TFT 15 formed therein, and the organic light emitting diode211 may further be formed on the plurality of interconnection layers.

(Configuration of Parts Above Light Emitting Element)

The opening 25 provided in the second member 52 of the organic lightemitting diode 211 is formed so as to have a tapered shape in which theside wall of the opening 25 is inclined such that the opening areaincreases with proximity to the bottom. Then, a first member 51 is putin the opening 25. That is, the first member 51 is a layer that isprovided immediately above the luminescence surface of the organic lightemitting diode 211 and that propagates emission light from the lightemitting element upward. Further, by forming the opening 25 of thesecond member 52 in the above manner, a cross-sectional shape in thestacking direction of the first member 51 (that is, the illustratedcross-sectional shape) has a substantially trapezoidal shape, and thusthe first member 51 has a truncated conical or pyramidal shape in whichthe bottom surface faces up.

The first member 51 is formed by forming Si_(1-x)N_(x) as a film by thevacuum vapor deposition method so as to fill the opening 25, and thenplanarizing the surface of the Si_(1-x)N_(x) film by the chemicalmechanical polishing method (CMP method) or the like. However, thematerial of the first member 51 is not limited to this example, andvarious materials having insulating properties may be used as thematerial of the first member 51. Examples of the material contained inthe first member 51 include Si_(1-x)N_(x), ITO, IZO, TiO₂, Nb₂O₅, abromine-containing polymer, a sulfur-containing polymer, atitanium-containing polymer, a zirconium-containing polymer, etc. Themethod for forming the first member 51 is not limited to this exampleeither, and various publicly known methods may be used as the method forforming the first member 51.

However, in the present embodiment, the materials of the first member 51and the second member 52 are selected such that the refractive index n₁of the first member 51 and the refractive index n₂ of the second member52 satisfy the relation of n₁>n₂. By selecting the materials of thefirst member 51 and the second member 52 such that the refractiveindices satisfy the relation mentioned above, at least a part of thelight that has propagated through the first member 51 is reflected at asurface of the second member 52 facing the first member 51. Morespecifically, the organic layer 23 and the second electrode 22 of theorganic light emitting diode 211 are formed between the first member 51and the second member 52, and therefore at least a part of the lightthat has propagated through the first member 51 is reflected at theinterface between the second member 52 and the organic layer 23. Thatis, the surface of the second member 52 facing the first member 51functions as a light reflection section (reflector) 53.

In the present embodiment, the first member 51 is provided immediatelyabove the luminescence surface of the organic light emitting diode 211,as mentioned above. Then, the first member 51 has a truncated conical orpyramidal shape in which the bottom surface faces up, and thereforelight emitted from the luminescence surface of the organic lightemitting diode 211 is reflected upward, which is the light emissiondirection, by the interface between the first member 51 and the secondmember 52, that is, the reflector 53. Thus, according to the presentembodiment, the efficiency of extracting emission light from the organiclight emitting diode 211 can be improved by providing the reflector 53,and the luminance as the entire display device 1 can be improved.

Note that an investigation by the present inventors shows that, toimprove the efficiency of extracting emission light from the organiclight emitting diode 211 more favorably, it is preferable that therefractive indices of the first member 51 and the second member 52satisfy the relation of n₁−n₂≥0.20. It is more preferable that therefractive indices of the first member 51 and the second member 52satisfy the relation of n₁− n₂≥0.30. Furthermore, to further improve theefficiency of extracting emission light from the organic light emittingdiode 211, it is preferable that the shape of the first member 51satisfy the relations of 0.5≤R₁/R₂≤0.8 and 0.5≤H/R₁≤0.8. Here, R₁represents the diameter of the light incidence surface of the firstmember 51 (that is, a surface facing down in the stacking direction andfacing the luminescence surface of the organic light emitting diode211), R₂ represents the diameter of the light emitting surface of thefirst member 51 (that is, a surface facing up in the stackingdirection), and H represents the distance between the bottom surface andthe upper surface (the height in the stacking direction) in a case wherethe first member 51 is regarded as a truncated cone or pyramid.

A protection film 31 and a planarizing film 32 are stacked in this orderon the planarized first member 51. The protection film 31 is formed by,for example, stacking Si_(1-y)N_(y) with a prescribed film thickness(approximately 3.0 μm) by the vacuum vapor deposition method. Further,the planarizing film 32 is formed by, for example, stacking SiO₂ with aprescribed film thickness (approximately 2.0 μm) by the CVD method andplanarizing the surface by the CMP method or the like.

However, the materials and the film thicknesses of the protection film31 and the planarizing film 32 are not limited to these examples, andthe protection film 31 and the planarizing film 32 may contain variouspublicly known materials used as a protection film and a planarizingfilm of a common organic EL display device so as to have filmthicknesses commonly employed in an organic EL display device, asappropriate.

However, in the present embodiment, it is preferable that the materialof the protection film 31 be selected such that the refractive index n₃of the protection film 31 is equal to the refractive index n₁ of thefirst member 51 or smaller than the refractive index n₁ of the firstmember 51. Furthermore, the materials of the protection film 31 and theplanarizing film 32 are selected such that the absolute value of thedifference between the refractive index n₃ of the protection film 31 andthe refractive index n₄ of the planarizing film 32 is preferably lessthan or equal to 0.30 and more preferably less than or equal to 0.20. Bythus selecting the materials of the protection film 31 and theplanarizing film 32, the reflection or scattering of emission light fromthe organic light emitting diode 211 at the interface between the firstmember 51 and the protection film 31 and the interface between theprotection film 31 and the planarizing film 32 can be suppressed, andlight extraction efficiency can be further improved.

The CF layer 33 is formed on the planarizing film 32. Thus, the displaydevice 1 is a display device of what is called an on-chip color filter(OCCF) system in which the CF layer 33 is formed on the first substrate11 on which the organic light emitting diode 211 is formed. The secondsubstrate 34 is stuck to the upper side of the CF layer 33 via, forexample, a sealing resin film 35 of an epoxy resin or the like, andthereby the display device 1 is fabricated. Note that the material ofthe sealing resin film 35 is not limited to this example, and thematerial of the sealing resin film 35 may be selected in view of hightransmissivity to the emission light from the organic light emittingdiode 211, excellence in adhesiveness to the CF layer 33 located on thelower side and the second substrate 34 located on the upper side, lowreflectivity of light at the interface with the CF layer 33 located onthe lower side and the interface with the second substrate 34 located onthe upper side, etc., as appropriate. However, the present embodiment isnot limited to this example. The display device 1 may be a displaydevice of what is called a facing CF system that is fabricated by the CFlayer 33 being formed on the second substrate 34, and the firstsubstrate 11 and the second substrate 34 being stuck together such thatthe CF layer 33 faces the organic light emitting diode 211.

The CF layer 33 is formed such that a CF of each color having aprescribed area is provided for each of the organic light emitting diode211. The CF layer 33 may be formed by performing exposure on a resistmaterial into a prescribed configuration and performing development byphotolithography technology, for example. Further, the film thickness ofthe CF layer 33 is approximately 2 μm, for example. However, thematerial, the formation method, and the film thickness of the CF layer33 are not limited to these examples, and the CF layer 33 may be formedso as to have a film thickness commonly employed in an organic ELdisplay device by using various publicly known materials that are usedas a CF layer of a common organic EL display device and various publiclyknown methods, as appropriate.

In the illustrated example, the CF layer 33 is provided such that a redCF 33R, a green CF 33G, and a blue CF 33B each having a prescribed areaare continuously distributed in the horizontal plane. Note that, in thefollowing description, in a case where there is no need to particularlydistinguish the CF 33R, the CF 33C; and the CF 33B, one or a pluralityof these may be written as simply a CF 33 a. One sub-pixel includes acombination of one organic light emitting diode 211 and one CF 33 a.

Hereinabove, a specific configuration example of the display device 1 isdescribed. Note that, in regard to the configuration of the displaydevice 1 described hereinabove, particularly the configuration of thereflector 53, JP 2013-191533A, which is a prior application by thepresent applicant, may be referred to, for example. However, theconfiguration of the display device 1 according to the presentembodiment is not limited to this example. As described above, it issufficient that the respects described in (4. Layout of interconnectionlayer) above be reflected in the display device 1 according to thepresent embodiment, and various known configurations used in ordinarydisplay devices may be used for the other respects.

(6. Application Examples)

Application examples of the display device 1 according to the presentembodiment described hereinabove will now be described. Herein, someexamples of electronic apparatuses in which the display device 1according to the present embodiment described hereinabove can be usedare described.

FIG. 14 is a diagram showing an external appearance of a smartphone thatis an example of the electronic apparatus in which the display device 1according to the present embodiment can be used. As shown in FIG. 14, asmartphone 501 includes an operation section 503 that includes a buttonand accepts an operation input by the user and a display section 505that displays various pieces of information. The display device 1 may beapplied to the display section 505.

FIGS. 15 and 16 are diagrams showing external appearances of a digitalcamera that is another example of the electronic apparatus in which thedisplay device 1 according to the present embodiment can be used. FIG.15 shows an external appearance of a digital camera 511 as seen from thefront side (the subject side), and FIG. 16 shows an external appearanceof the digital camera 511 as seen from the rear side. As shown in FIGS.15 and 16, the digital camera 511 includes a main body section (camerabody) 513, a replaceable lens unit 515, a grip section 517 that isgripped by the user during photographing, a monitor 519 that displaysvarious pieces of information, and an electronic view finder (EVF) 521that displays a through image that is observed by the user duringphotographing. The display device 1 may be applied to the monitor 519and the EVF 521.

FIG. 17 is a diagram showing an external appearance of a head mounteddisplay (HMD) that is another example of the electronic apparatus inwhich the display device 1 according to the present embodiment can beused. As shown in FIG. 17, an HMD 531 includes an eyeglass-type displaysection 533 that displays various pieces of information and ear-fixingsections 535 that are fixed to the user's ears during wearing. Thedisplay device 1 may be applied to the display section 533.

Hereinabove, some examples of the electronic apparatus in which thedisplay device 1 according to the present embodiment can be used aredescribed. Note that the electronic apparatus in which the displaydevice 1 can be used is not limited to those described above asexamples, and the display device 1 can be used for display devices thatare mounted on electronic apparatuses in all fields that perform displayon the basis of an image signal inputted from the outside or an imagesignal generated in the inside, such as a television device, anelectronic book, a smart phone, a personal digital assistant (PDA), anotebook personal computer (PC), a video camera, and a game apparatus.

(7. Supplement)

The preferred embodiment (s) of the present disclosure has/have beendescribed above with reference to the accompanying drawings, whilst thepresent disclosure is not limited to the above examples. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present disclosure.

For example, although in the embodiment described above each of thetransistors (the driving transistor 212, the sampling transistor 213,the light emission control transistor 214, and the switching transistor217) included in the driving circuit of the pixel circuit 210 is of aP-channel type, the technology according to the present disclosure isnot limited to this example. For example, each of these transistors maybe of an N-channel type.

Further, the effects described in this specification are merelyillustrative or exemplified effects, and are not limitative. That is,with or in the place of the above effects, the technology according tothe present disclosure may achieve other effects that are clear to thoseskilled in the art from the description of this specification.

Additionally, the present technology may also be configured as below.

(1)

A display device including:

a pixel unit which is configured with a plurality of pixel circuitsarranged in a matrix, each of the pixel circuits including a lightemitting element and a driving circuit for driving the light emittingelement;

scanning lines which are interconnections connected to the respectivepixel circuits and are provided to extend in a first direction andcorrespond to respective rows of a plurality of the pixel circuits; and

signal lines which are interconnections connected to the respectivepixel circuits and are provided to extend in a second directionorthogonal to the first direction and correspond to respective columnsof a plurality of the pixel circuits,

in which one of the scanning lines and the signal lines, provided forthe one pixel circuit, which is larger in number is positioned in alower-level interconnection layer, and

an electrode of a capacitance element included in the driving circuit ispositioned in the interconnection layer in which either the scanninglines or the signal lines are provided.

(2)

The display device according to (1),

in which the driving circuit includes a plurality of transistors, and

a plurality of interconnection layers each having the scanning lines,the signal lines, and the capacitance element formed therein are stackedon a diffusion layer in which a plurality of the transistors are formed.

(3)

The display device according to (2),

in which the light emitting element is an organic light emitting diode,and

the organic light emitting diode is positioned on the interconnectionlayer of an uppermost layer.

(4)

The display device according to any one of (1) to (3),

in which one sub-pixel includes the one pixel circuit, and one pixelincludes the four sub-pixels.

(5)

The display device according to any one of (1) to (4),

in which the number of the scanning lines is larger than the number ofthe signal lines.

(6)

The display device according to any one of (1) to (5),

in which the scanning lines are interconnections extending in ahorizontal direction, and

the signal lines are interconnections extending in a vertical direction.

(7)

The display device according to any one of (1) to (6),

in which all of a plurality of the scanning lines are positioned in asame interconnection layer or all of a plurality of the signal lines arepositioned in a same interconnection layer.

(8)

The display device according to any one of (1) to (7),

in which a plurality of the scanning lines are disposed to be dispersedin a plurality of different interconnection layers or a plurality of thesignal lines are disposed to be dispersed in a plurality of differentinterconnection layers.

(9)

An electronic apparatus including:

a display device which performs display on the basis of a video signal,

in which the display device includes

a pixel unit which is configured with a plurality of pixel circuitsarranged in a matrix, each of the pixel circuits including a lightemitting element and a driving circuit for driving the light emittingelement,

scanning lines which are interconnections connected to the respectivepixel circuits and are provided to extend in a first direction andcorrespond to respective rows of a plurality of the pixel circuits, and

signal lines which are interconnections connected to the respectivepixel circuits and are provided to extend in a second directionorthogonal to the first direction and correspond to respective columnsof a plurality of the pixel circuits,

one of the scanning lines and the signal lines, provided for the onepixel circuit, which is larger in number is positioned in a lower-levelinterconnection layer, and

an electrode of a capacitance element included in the driving circuit ispositioned in the interconnection layer in which either the scanninglines or the signal lines are provided.

REFERENCE SIGNS LIST

-   1 display device-   10 display panel-   20 pixel unit-   30 scanning unit-   40 selection unit-   210, 220 pixel circuit-   211, 221 organic light emitting diode-   212 driving transistor-   213 sampling transistor-   214 light emission control transistor-   215, 227 holding capacitance-   216 auxiliary capacitance-   217 switching transistor-   222, 223, 224, 225, 226 transistor-   228 H scanning line-   229 V signal line-   231 diffusion layer-   232, 235, 238, 241 insulating layer-   233 contact-   236, 239, 242 via-   234, 237, 240 interconnection layer-   243 anode-   251 capacitance element lower electrode-   252, 254 capacitance element upper electrode-   261 organic layer-   301 writing scanning unit-   302 writing scanning line-   311 first driving scanning unit-   312 first driving line-   321 second driving scanning unit-   322 second driving line-   331 common power supply line-   332 power supply line-   333 ground line-   401 signal output unit-   402 signal line-   501 smartphone (electronic apparatus)-   511 digital camera (electronic apparatus)-   531 HMD (electronic apparatus)

The invention claimed is:
 1. A display device comprising: a plurality ofpixel circuits arranged in a matrix having a row direction and a columndirection, each of the pixel circuits including a light emitting elementand a driving circuit for driving the light emitting element, thedriving circuit including a capacitive element; scanning lines connectedto the respective pixel circuits and extending in the row direction; andsignal lines connected to the respective pixel circuits and extending inthe column direction, wherein for at least one of the pixel circuits,the number of scanning lines is larger than the number signal lines, atleast one of the scanning lines is located in a first interconnectionlayer, at least one of the signal lines is located in a secondinterconnection layer, the first interconnection layer being locatedlower than the second interconnection layer in a cross sectionperspective, and a first electrode of the capacitance element is locatedin the second interconnection layer.
 2. The display device according toclaim 1, wherein the driving circuit includes a plurality oftransistors, and the first and second interconnection layers are stackedon a diffusion layer in which the plurality of transistors are formed.3. The display device according to claim 2, wherein the light emittingelement is an organic light emitting diode, and the organic lightemitting diode is positioned on another interconnection layer of anuppermost layer.
 4. The display device according to claim 1, whereinsaid at least one of the pixel circuits includes the four sub-pixels. 5.The display device according to claim 1, wherein all of the scanninglines are positioned in the first interconnection layer and all of thesignal lines are positioned in the second interconnection layer.
 6. Thedisplay device according to claim 1, wherein the scanning lines arerespectively disposed in a plurality of different interconnection layersor the signal lines are respectively disposed in a plurality ofdifferent interconnection layers.
 7. The display device according toclaim 1, wherein a second electrode of the capacitance element islocated in a third interconnection layer that is located higher than thesecond interconnection layer in the cross section perspective.
 8. Anelectronic apparatus comprising: a display device which performs displayon a basis of a video signal, wherein the display device includes aplurality of pixel circuits arranged in a matrix having a row directionand a column direction, each of the pixel circuits including a lightemitting element and a driving circuit for driving the light emittingelement, the driving circuit including a capacitive element; scanninglines connected to the respective pixel circuits and extending in therow direction; and signal lines connected to the respective pixelcircuits and extending in the column direction, wherein for at least oneof the pixel circuits, the number of scanning lines is larger than thenumber of signal lines, at least one of the scanning lines is located ina first interconnection layer, at least one of the signal lines islocated in a second interconnection layer, the first interconnectionlayer being located lower than the second interconnection layer in across section perspective, and a first electrode of the capacitanceelement is located in the second interconnection layer.
 9. Theelectronic apparatus according to claim 8, wherein the driving circuitincludes a plurality of transistors, and the first and secondinterconnection layers are stacked on a diffusion layer in which theplurality of transistors are formed.
 10. The electronic apparatusaccording to claim 9, wherein the light emitting element is an organiclight emitting diode, and the organic light emitting diode is positionedon another interconnection layer of an uppermost layer.
 11. Theelectronic apparatus according to claim 8, wherein said at least one ofthe pixel circuits includes the four sub-pixels.
 12. The electronicapparatus according to claim 8, wherein all of the scanning lines arepositioned in the first interconnection layer and all of the signallines are positioned in the second interconnection layer.
 13. Theelectronic apparatus according to claim 8, wherein the scanning linesare respectively disposed in a plurality of different interconnectionlayers or the signal lines are respectively disposed in a plurality ofdifferent interconnection layers.
 14. The electronic apparatus accordingto claim 8, wherein a second electrode of the capacitance element islocated in a third interconnection layer that is located higher than thesecond interconnection layer in the cross section perspective.